69 Dart Qtr window parts needed

[JOES4FORTY]

I have a 69 Dart GTS. Looking down inside the rear window channel you can see a rear track and a ball. There is a part that fits on the ball that slides the rear of the window on the track. Mine are missing. I'll need both the drivers and passenger side. It's supposed to be a white plastic block? Look at the photo. Thanks, Joe

JOES4FORTY@yahoo.com