I used emmett's OpenSCAD file to create the planetary gears >> https://www.thingiverse.com/thing:53451
It uses 3 8mm(D)x3mm(H) magnets. The center magnet needs to be glued in place. The outer magnets should be press-in, but can be glued if needed. The 2 outer magnets are to keep the outer part from spinning. They attract to the screws in the corners of the motor.
I also included an MMU 4 color version. It should look a lot better with multi-color.
* Edit
Shortened the post where the middle magnet mounts. It was pushing the Sun gear out too far and causing minor friction.
The author remixed this model.