85 300sd Power Window Issues

[mdf300sd]

Both my rear window motors work as they should but the little 2 piece bit of plastic that rides in the slider rail has broken so it will not hold the arm in place, I looked at it briefly but it did not seem serviceable. Or maybe the stud unthreads from the arm to allow me to snap in a new plastic slider piece. Am i right or do I need to replace the entire unit.

Thanks everyone for your time.
Matthew