Many users have requested to purchase the custom thumb keycaps that Dygma keyboards mount. Unfortunately, we're not keycap manufacturers; we only have the molds to create whole sets, and we have to sell them as such. Otherwise, we would have to discard the rest of the set to sell the thumb keys separately.
Nonetheless, if your keycaps are damaged and the keyboard is under warranty, email us at support@dygma.com, and we'll provide a solution.
If you have a 3D printer, you can also print them yourself. You can find the STL files here: