Welcome to Geekhack!
Oooo there's lots of non-standard size keycaps on that keyboard

That will make finding a replacement keycap set much more difficult, unfortunately.
There are a few 3D printed keycaps around, but most artisans tend to hand-carve theirs and/or use some sort of injection molding.
Your best bet is to have a look through the
media section and see if any artisans catch your eye. Then look for upcoming sales in the respective sub-forum in the
artisan services section.