Lots of options:
https://www.havalon.com/piranta-blades
Looks like they ship with a standard form scalpel blade, #60.
Havalon 60A is the thick one, 60XT is the thinner one. Both are available in smaller quantities than the packs linked below.
60A
https://www.amazon.com/Havalon-Stain...dp/B00F7FLS0E/
60XT
https://www.amazon.com/Havalon-Stain...dp/B00D79EODK/
The reviews say the same blades work in the Gerber handle.
Thanks, this has been an educational bit of the afternoon. I had no idea those knives existed. I like the weight, cost and serviceability a heck of a lot better than what is usually discussed for skinning/dressing knives.