My old DIY handle made from a soda bottle broke so I designed this to replace it based on my original. I use wall gum/tac adhesive but I left a hole for placing a magnet as well if that's your preferred attaching method.

Printing

no supports, 20% infill, PLA, no brim, 0.2 height

Assembly

The cap is hard to attach to the base so I recommend placing it on the floor and stepping on it. The additional rings around the base are for stability, you need to insert the cap fully. The arm can be glued or friction fitted, I didn't use glue so I can change the arms.

Let me know if you want some custom arms.