FYI, here's another version:
https://www.thingiverse.com/thing:4234854
That one has been re-enforced around common breaking points.
You can order one printed in nylon here:
https://www.shapeways.com/product/2D...e-clip-v02-011
The original one appear to be nylon, and as you said you printing in a strong material is important.
Good luck!
Ian.