I needed a zipper pull that could use a larger paperclip than the ones I was finding. I measured my clip and built a parametrized design based on the paperclip measurements. I haven't tried it with other clip sizes, but if you have a different sized clip you may be able to adjust the parameters by editing the scad file. Note that the Customizer doesn't seem to work with my scad file---it produces a weird result.
The two halves snap together nicely for me, but not securely enough for use. I glued my PETG version together using thick 2p-10 cyanoacrylate adhesive.
Two design considerations were making the zipper pull centered on the mounting end of the paperclip and giving it eased edges.