Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:3529597.

My conditions were to be as small as possible and be secure. The 3.5 plug type didn't really hold on the well even though I did love the size. The other ones that held are securely were either wide or thick.

I did print with supports for the nub, Keep in mind you'll need an excato or another extremely small tool to get the support out. I sliced with Slic3r so if you're using cura you may want to make custom support.