I hope to be able to replace parts frequently and avoid loosening caused by plastic wear. The magnetic solution seems to be the best choice. I specifically designed a cavity that can embed a 5 mm diameter and 3 mm thick round neodymium-iron-boron magnet, and fixed it securely with a drop of quick-drying glue.

I've attached the OpenScad file I wrote to add the concave cavity to the original 4volt .stl file. With just a few adjustments, it can easily be adapted to different sizes of round magnets. The entire script simply removes a cylinder from the original model, so you need to download the original 4volt file to the same directory as the OpenScad file to run it properly. The file includes detailed comments on the relevant parameters and operating steps.

For users who are not familiar with OpenScad, if you need the .stl file of a specific model of magnet, please feel free to leave a comment in the comment section. I will upload it for you as soon as I have time.