Update: I have now got around to printing this and the M was way too small and also didn't even fit. No one told me, but now I fixed it.
The only thing I changed from the original "Pokeball, with magnetic clasp" was the lid.
Print the Lid, M, BumpTopLeft and BumpTopRigh (right/left with button facing towards you). The two Bump files in theory should be the same but just in case I provided both.
After printing the parts you should be able to easily assemble the lid. From there glue the button into the button holder. Then glue the button assembly and the ring to the bottom with the hinge in place as you glue the ring down. Then snap the hinge into the lid.
You will need 2 magnets (1/4" X 1/16") and just glue them in place too.
Tip: Print your bottom piece at a higher in fill percentage, around 40-50% and then all the other parts at 5-10%. That way it will be bottom heavy and not roll around as much.