Preserving Human Toe

Hello! I am not a taxidermist, but a cadaver-dog trainer sent me here thinking I could find help! This is an odd request! My friend recently had a toe amputated, and kept it! He wants to preserve it (probably to spook his grand-kids), but isn't sure how to go about it. It's currently in denatured alcohol. I was tracking down formalin for it, but then wasn't sure exactly what to do if I found some.

Can anyone give me an idea on how to preserve the little guy? Can I just soak him in 10% formalin? Any insight would help! I've never done anything like this before. My friend is elderly and searching the inter-webs isn't quite in his grasp--hence me helping!

Thank you!!