I built a second set of wheels for my Promoto and realized I'd have to buy a brake rotor to complete the look - but it doesn't actually do anything except make it look more realistic!
So here ya go - it's a Promoto-compatible rear brake rotor.
Print with 6+ walls. It doesn't take much abuse where it's situated so PLA should do the trick.
The author marked this model as their own original creation.