elbow magnet
thingiverse
https://patents.google.com/patent/US5929732 use that to push it in to place print outside magnet... and buy a sphere magnet
Download Model from thingiverse
With this file you will be able to print elbow magnet with your 3D printer. Click on the button and save the file on your computer to work, edit or customize your design. You can also find more 3D designs for printers on elbow magnet.