customizations to paid assets in a git repo

I ran into a situation with one of my games, where I needed to make modifications to some paid assets that I got. Animations here and there, Bone adjustments, etc. I didn't want to put them on github because then the paid assets would be out there in the world.

Aside from private repos, is there any other good practice that people have done to customize their paid assets and keep them in git, or source control, without spreading them out to the world?