Door glass track

This is on a 68 Dart 2dr hard top.

I took my door apart, and the vent window track plastic, the window is held in with came apart. Where can I get a new one? These doors are off a parts car, and the rubber stop that is sandwitched in the vent window that the door glass hits when you roll it up is missing. Where can I get a new rubber stop? This looks like a lot of fun to put back together...anyone have any pointers on putting it all back together.