1) How do you guys find part numbers for these tiny parts?

2) The part I need is a plastic washer that goes over the power seat control for the seat back. This is a stock photo, so it's NOT at the red arrow, but just down and left of the green button. On that round stub there's a plastic washer that goes over it. I guess its job is to keep the entire plastic trim piece around these controls from moving forward.

https://cdn4.pelicanparts.com/techarticles/Mercedes-W124/120-ELEC-Power_Seat_Control_Switch_Replacement/images_med/pic03.jpg

1991 300d

Go to your local big box hardware store and look through their plastic washer assortment.

Is it a washer? I thought it was more of a circlip. For that you need EPC. Or go to the pick-n-pull for as many as you’ll need.

Sixto
98 E320 sedan and wagon

Pull the whole switch from the yard or look for an alternate at hardware store. A dealer may have them. Shipping is more than the Part. Still, buying will be easier than finding at a yard.

Yards are great but you only get what happens to be there.

Hardware stores also have circlip assortments if that what it is. One does not always need Mercedes OE for every little thing.