A short flat-head M3 screw fixes the handle to the magnet. M3 thread is printed inside the hole, but re-cutting will improve it. The scad file is configured for the smaller size, but the other values are still present as comment.
The handles are printed in PLA, as this is easy and the variation in colors is largest. Printed with a Prusa MINI+.
The author hasn't provided the model origin yet.