These are based on common commercialy available clips. I went through about 10 iterations of the design to find what will work with 3d printing material. I tried to find a balance between to weak and to strong and spring. I printed in both PLA and PET and found PET to give the best result.

100% infill
.15mm resolution
.4 nozzle dia.
1.75 filament
PET
Supports needed (Not needed for hole)

You may need to break free the clip jaws from eachother. I just give them a firm twist or use needle nose pliers in the clip jaws and spread the pliers to free the jaws.