I’ve been a similar situation before, so sorry for the long post!
First, for non-official stuff, I think some metallic sword and shield charms could be really cute if you could find them! I also think a pale yellow backing would help bring out the gold in its design. You can also make your own pieces with official art, sprites, or screencaps of its anime appearances, though sprites might be hard for aegi since it was introduces as they were phased out for models. There’s also always fanmerch—have you checked storenvy, etsy and tictail? Redbubble also sometimes has some nice big stickers that you can turn into pins, just make sure you do something about the white space on them.
For official stuff, every pokemon out now has a small (like ~1-1.5cm) metal charm, and they’re sold in sets by evolution line. I checked the jp pokecenter site and it’s is sold out, thankfully suruga-ya has it! I also found a keychain on otamart that looks like it was a capsule prize. There’s also pan and wafer seals, which are the things along the top of my pic. There about 2x2” and you can slide them into card sleeves to cover the text part of the cards nicely! The pan seals are the ones with the plain white backing, and they look a lot nicer if you trim them or do something to minimize the white. Lastly, there have been these collectible tokens that have been made to use with arcade games which you could easily just glue a pin to. Aegi has a handful for the first one that was called pokemon treta, and a couple are pictured on the right. As you can see though, their border colors don’t always match the pokemon exactly. I don’t have any of the treta tokens, but I’m guessing they’re about the same size as the seals based on the ones I do have.
I just slapped the links of what I found here in a pastebin so I won’t upset the small filter. If you want to do any more hunting, it’s Japanese name is ギルガルド ! https://pastebin.com/D5gtrP1H