Rustpot
M Frame Lover
I wanted to fix my broken New Frogskin. I looked into trying to make a mold of the stem and trying to find some plastic to mold my own replacement stems. Later I saw that people can do a 3D scan and print plastic parts via 3D printer. From what I've read, people can print plastic parts using ABS plastic, polycarbonate, or nylon.
Several have been popping up on eBay for $25-80, it would probably cost a lot less to buy a new pair.