My motorcycle jacket is well past its end of life but I keep it on support. The original metal zipper slider (aka car) started bending internally until finally it wouldn’t work any more. I replaced it with a 3D printed version. Modeled in FreeCAD. Printed in PLA+. I planned to print in something else but as usual PLA turned out more robust than I expected, it has been years since I replaced it. It’s better than the original metal part.

This design is on printables as well.