Help me locate this part - Window stabilizer guide

If you contact glue felt over those they last another 40 years. :D
Several members including myself have fixed them this way over the years.

That's a great idea. Let me add this, I have an expensive window film applied to the windows to cut the solar heat from the sun here in Florida (3M Crystalline). It scratches easily and I am concerned that the window rubbing on the felt, even under some slight pressure, over time may cause a band of fine scratches in the film that will look like a dull band. Is this small part really necessary? The window seems fine without it. Not loose or wobbling. Can I leave it out?