Got this problem with the mk6 Fiesta as well. Spoke to ford, and it is a common fault. They at this time do not sell the plastic gear seperately. Infact they only sell the motor with the regulator, and the large plastic door panel. The blue geared ones are for the 3dr, and the white geared ones are for 5dr version, but they are not interchangable. They are also rare in scrap yards to. I'm going to try to strip a broken drivers side one, to see if it is repairable with parts from a passenger side one.