Flats tend to make up a lot of the merch that Wimpod and Golisopod get. Most only have them as cameos, but some items do feature them more prominently.

Rainbow Rocket Guzma & Golisopod Clearfile
Manufacturer: Pokémon Center (Japan)
Product Line: Rainbow Rocket Secret Teams
Release Date: January 20 2018
Purchased From: PKMNCollectors
This clearfile could only be purchased in a set with all the others in the series, but someone was kind enough to sell me just this one. Mine is so shiny because it's still sealed in the packaging it came in.

Rainbow Rocket Guzma & Golisopod Postcard
Manufacturer: Pokémon Center (Japan)
Product Line: Rainbow Rocket Secret Teams
Release Date: January 20 2018
Purchased From: PKMNCollectors
I got this from the same person as the above clearfile. It's way easier to see the art on this one, despite it also being sealed.

Rainbow Rocket Team Skull Stickers
Manufacturer: Pokémon Center (Japan)
Product Line: Rainbow Rocket Secret Teams
Release Date: January 20 2018
Purchased From: Mercari Japan
These stickers feature Guzma and Golisopod, the Team Skull logo, and the team's name in Japanese. I wish the packaging wasn't bent, but the stickers themselves don't seem to be affected so it's all good.

Comic Book Pages featuring Wimpod
Manufacturer: ???
Product Line: ???
Release Date: 2017?
Purchased From: PKMNCollectors
These were part of a large lot of Wimpod/Golisopod related flats that were sold to me. Wimpod looks so adorable in them!
If anyone here can read Japanese and would be willing to translate these for me, please let me know!

Book Pages featuring Wimpod & Golisopod
Manufacturer: ???
Product Line: ???
Release Date: 2017?
Purchased From: PKMNCollectors
Part of the same lot as the comic pages above. These were probably from Sun & Moon strategy guides or Pokédex books.

Wimpod & Golisopod Pan Stickers
Manufacturer: Daiichi Pan (Japan)
Product Line: Pokémon Pan
Release Date: 2017?
Purchased From: PKMNCollectors
You could get these with snacks in 7-11 stores across Japan. Pretty much every Pokémon has at least one at this point.
There may be a few variations of these out there that I don't have, but I'm not really sure.

Wimpod & Golisopod Ga-Olé Disks
Manufacturer: Takara Tomy A.R.T.S. & Marvelous (Japan)
Product Line: Ga-Olé Dash Set 5
Release Date: April 26 2018
Purchased From: Mercari Japan
These are used to play the Pokémon Ga-Olé game originally in Japan, and now in a few other countries as well. Not sure if the disks you can get there are any different from the ones I have, or if they've even been released there, but I plan on getting 'em if I find out they exist.

Wimpod Ga-Olé Disk (Chinese Version)
Manufacturer: ??? (China)
Product Line: ???
Release Date: ???
Purchased From: Discord
Turns out that Wimpod (and presumably Golisopod) did get their Ga-Olé disks released elsewhere! They're pretty similar to the originals, save for all the text being written in Mandarin Chinese rather than Japanese.
Click here to see the two versions side by side.

Wimpod & Golisopod Mezastar Tags
Manufacturer: Takara Tomy A.R.T.S. & Marvelous (Japan)
Product Line: Mezastar Set 2
Release Date: November 26 2020
Purchased From: Mercari Japan
Used when playing the Pokémon Mezastar game, which is a successor to Ga-Olé and currently only available in Japan. I hope that more end up being made for Wimpod and Golisopod in future sets, as only seeing them once in Ga-Olé was a bit disappointing.

Wimpod & Golisopod Mezastar Tags (Super Tag Set 4)
Manufacturer: Takara Tomy A.R.T.S. & Marvelous (Japan)
Product Line: Mezastar Super Tag Set 4
Release Date: February 10 2022
Purchased From: Mercari Japan
Wish I could go back in time and tell my past self about these; not only did Wimpod and Golisopod get more Mezastar tags, but the renders on these are even cooler! I especially love the Wimpod; you rarely see official art of him that doesn't use the same scared expression. But that's not all...

Golisopod & Sylveon Mezastar Tag
Manufacturer: Takara Tomy A.R.T.S. & Marvelous (Japan)
Product Line: Mezastar Super Tag Set 4
Release Date: February 10 2022
Purchased From: Mercari Japan
The Mezastar Super Tag sets began intoducing tags that featured a main Pokémon and a helper, and Golisopod actually got one with Sylveon as his partner! This is so, so cute; I love it when "scary" and "cute" Pokémon are shown together being friends.

Black Tapu Koko Clearfile featuring Golisopod
Manufacturer: Pokémon Center (Japan)
Product Line: Black Tapu Koko
Release Date: March 18 2017
Purchased From: PKMNCollectors
I love the art on this clearfile; it's way more colorful and shiny than in this picture. Fun fact: with the release of Ultra Sun & Moon, every Pokémon featured in this merch line got their own Z-Move... except Golisopod. :(

Wimpod & Golisopod Pogs
Manufacturer: ??? (Korea)
Product Line: ???
Release Date: ???
Purchased From: PKMNCollectors
I suspect that these are used for some sort of game given the stats on them, but I don't know what exactly. All I know is that they were blind-boxed and that there may be more variants out there I haven't seen yet. There's not a lot of English-language resources for non-English/Japanese Pokémon merch out there from what I've seen, so I have to do a lot of guessing...

Bug Z-Move Card featuring Golisopod
Manufacturer: ??? (Japan)
Product Line: ???
Release Date: ???
Purchased From: Mercari Japan
This card features a screenshot of the male Ultra Sun & Moon protagonist doing the Bug-type Z-Move pose, along with stock art of Golisopod, Araquanid, and Butterfree. There's a QR code on the back along with some art of Mythical Pokémon that I believe may give you those Pokémon in a Gen 7 game, but I'm not sure.

Sparkly Gen 7 Stickers featuring Golisopod
Manufacturer: ??? (Korea)
Product Line: ???
Release Date: ???
Purchased From: Discord
These stickers seems to be themed around the Pokémon anime, given the logo in the top left. Grubbin, Rowlet and Pyukumuku, three other Gen 7 'mons I love, are there as well, which is nice.

Wimpod & Alolan Exeggutor Sticker Card
Manufacturer: ??? (Japan)
Product Line: ???
Release Date: ???
Purchased From: PKMNCollectors
This sheet is slightly bigger than a regular Pokémon card, and features Wimpod and Alolan Exeggutor together. This is probably because of the anime episode SM020, which has an Exeggutor rescue Ash and a wild Wimpod from a pit they fell into. It's nice to see Wimpod with a friend! Also, Ash totally should have caught them.

Hyaku Poke Yako Sticker Sheet featuring Golisopod
Manufacturer: Pokémon Center (Japan)
Product Line: Hyaku Poke Yako
Release Date: July 13 2018
Purchased From: Mercari Japan
Features most of the Pokémon that are focused on in the Hyaku Poke Yako line. It took me a ridiculously long time to find these, which was a bit surprising.

Sun & Moon Coloring Book featuring Golisopod
Manufacturer: ??? (Japan)
Product Line: N/A
Release Date: ???
Purchased From: Discord
This uses some of the same art as other late Sun & Moon era merchandise. What particularly excited me about it is that the Golisopod art used is rarely seen anywhere else, with no full version easily accessible. This book contains the closest thing we currently have to the full art, albeit without any color.
Click here to see the front of the book, and here to see the Golisopod page.

Bug Z-Move Sticker featuring Golisopod
Manufacturer: ??? (Japan)
Product Line: ???
Release Date: ???
Purchased From: Mercari Japan
This was probably made around the same time as the Z-Move card shown previously. It is two stickers stuck to the same backing, the other of which has the male protagonist from Ultra Sun & Ultra Moon.
Click here to see the back of the sticker.

Ultra Sun Sticket Sheet featuring Golisopod
Manufacturer: ??? (Korea)
Product Line: ???
Release Date: ???
Purchased From: PKMNCollectors
I had to buy the entire set this sheet was included in just to get it. It comes with a little booklet featuring the same art of all the included 'mons, plus a bunch of other Gen 7 stickers.

Wimpod & Golisopod Book Page & Stickers
Manufacturer: ??? (USA)
Product Line: N/A
Release Date: 2022
Purchased From: Discord
These come from a sticker book that I believe had at least one sticker for every Pokémon. I don't think I've ever seen that Golisopod art before!

Golisopod Chocolate Snack Wrapper
Manufacturer: Tohato (Japan)
Product Line: N/A
Release Date: ???
Purchased From: Discord
This contained what I believe was similar to a chocolate Rice Krispies treat. I had the actual food removed before it was sent to me, as I imagine it would have gone bad at this point.

Rainbow Rocket Golisopod Mini Sticker
Manufacturer: Pokémon Center (Japan)
Product Line: Rainbow Rocket Secret Teams / Boss Gokko Pikachu
Release Date: January 20 2018
Purchased From: Mercari Japan