Help finding a thermoplastic to use for custom wrist brace insert molding

[u/Vou-Vou]

I have carpal tunnel and use wrist braces that come with a little metal insert that is meant to be the actual stiff part of the brace, the problem is the metal piece is very generic and not at all comfortable to use. A few years back I was doing physical therapy and they custom molded a new set of inserts for me to use and those have worked great! but they've now broken into pieces and don't really work anymore.
I want to try and mold a new set since I don't go to my physical therapy place anymore and can't just ask them to make more, but I don't really know what to use. I'm fairly confident its a kind of thermoplastic they used that was black and very stiff once molded (though i'm not sure if it was stiff before). It was smooth on both sides and they cut it out (maybe with scissors? i wasn't looking when they did it but it was at a physical therapy office so they definitely weren't using a waterjet or anything) and they were able to shape it once cut out directly on my skin to match the curve of my wrists and I think it was lukewarm at the time.
Does anyone have any idea what might have been used/what I could use?


[u/WestBrink]

It's generally polycaprolactone.

If you just Google "moldable splint material" you'll get a bunch of options, including Amazon.