Where can I get...a ThumbRing in the US?

You can get them from eastern-archery.com, But thats out of finland. I've ordered one from their. But you can get them from spitfire horsebows. I don't have the address right , I'm sure you can run an search and get it, If not tell me and I'll get it for you.

#rivers archery also sells them in their primitive section.

Correction, I should have read what I wrote first.....It is 3riversarchery.com

Hey! Why not make one for yourself. It is fun! You will like it more because that's your work. And when you make the second ,the third one it will get better and better.
That's fun.

I actually built both of mine from poolball, this picture is one. I do want to build the next from horn, But I have to find some first.

Matt