- r3drckt Goblin Guru
@k.rollin linked the ones from the DF store above. If you have a 3d printer, you could make your own as well. Open your choice of design software, make a solid circle that's the size of rotor's opening, then cut a circle hole the size of the wheel hub out of that solid, export to your slicing software and then print. If I had to guess, the print would take all of about 10-15 minutes to do.