A design of a magnetic cable arch I made. Magnets can be attached in the bottom holes to hold them to something magnetic.

You can print them with supports, i used tree supports and with the magnet holes facing down. I used 16x5mm magnets from amazon with screw holes. You can press fit them, but if they are too lose just screw them in.

I made them in three sizes:

Small 49 x 13 mm 

Medium: 67X18mm

Large: 82 x26mm

FYI: These are also on printables