Sketched on my drawing tablet and then created the 3mf file with Fusion 360.

Magnets used: diameter 6 mm, height 3 mm (strong magnetic force). If the fit is too tight, simply warm it up briefly with a lighter and press it in. Secure with glue if necessary.

There is also a flat version to use adhesive magnets (light magnetic force).

3mf files are from orcaslicer!

take a look at the matching cat https://www.makeronline.com/en/model/Hungry%20Cat%20Fridge%20Magnet/18024.html

…have fun printing!