Power window track roller assembly needed! or parts help needed?

All: working some bugs out of my rear quarter power window assembly while winter is upon us. 67 Chrysler 300 rag top. Glass was sagging inwards and upon removal I found that the plastic roller on one side of the track slot was broken. I am hesitant to ask if this is a replaceable part, or does one buy the roller and retrofit? Any suggestions would be much appreciated as usual! Cam Shaft