A simple light phone case “rubber bumper” style.

Thick enough to absorb the bumps. Minimal and light. 
Thin enough to charge wirelessly.

Verified fit, works well.

Version 3.3 and later add handgrip notches, and has a less pronounced lip on the back side (easier to hold).  
 

All versions print with a support included. Cut it out or pull it off after printing.

Added a .f3d Fusion 360 source file if you want to make a mod/remix.

Apologies for the washed out pictures It's hard to take a picture of your phone without your phone.

Printed in SainSmart TPU at 0.15LH with no supports, 100% infill, on a Mk3S+.