power window regulator part id question

What is the white plastic piece that is circled?
My passengers side regulator is missing this piece and I need to know what to ask for.

Yes I would like to know also and where to get one. My window regulator also needs one.

Good luck with that... You'll likely be cutting up regulators to get it if your able to find one...

I can live without it if that is the case.
Its been clunking for years and I thought it may be simple to fix before reassembly.

I think that part is kinda like the thrust button on a roller cam, it's a rub button keeps the gear in place.