Universal Phone Tripod Mount. Should work for screen sizes from 4" to 6". It is designed to inprint M6 nut. At the end of layer 23 you have to insert ...the nut (with 0.3 layer height). Second thing you need is a rubber band.
Things you need:
M6 Nut
Any rubber band
This thing is made in onshape, and it's fully customizable.