I remixed this from https://www.thingiverse.com/thing:910216 - the original doesn't have much pinch, but I added holes so the spring from a click pen could be added! With the additional biting force, the clip is much more useful.
I used the spring from a regular bic pen - it's 0.96" tall and has a diameter of 0.175". The holes in the shark for holding the spring I modeled at 0.2" diameter, but depending on your printer it could be smaller.
sharkz_spring_opt.stl | 747.5KB |