Thumb brace for fixation of the 2nd thumb joint. I designed the brace when I dislocated my thumb while climbing. It works pretty well for me, but I have small hands. You can just change the scale to make it fit you properly. If you extend the bracer, you should be able to fixate the first thumb joint too. 

You can put a puller or velcro on the grooves for a better attachment of the orthosis to the hand. I didn't need it; the brace fit perfectly and stayed on my hand by itself.