These are simple pinboard magnets. In fact you don't need a 3D-Printer for it - hotglue is maybe also fine. But with a 3D printed body it is even better :)
It's nice to use the rest of a filament spool!
This is a work in progress project for me. I designed it with OpenSCAD ~~and plan to publish my source file as well in the future~~. The source code is available on Codeberg, but still need some work. With this it should be adoptable to all kind of threaded bottle caps and magnet with another size.
Printer Brand:
Anet
Printer:
A8
Rafts:
No
Resolution:
0.15
Insert the Magnet
Insert the magnet in the middle and put the little cap an it.
Turn Cap
On the bottom of the buddy are two small holes. Put a paper clip inside. Use the paper clip to turn the whole printed body into the cap.

The author marked this model as their own original creation. Imported from Thingiverse.