Old mounting bracket/slider for drawer?

I'm trying to find out anything about the bracket that *should* be in the very back of the track on the underside of the drawer. The pictures are of the drawer that is complete. There's another one missing that small plastic piece which slides into the track under the drawer.

I've jury-rigged a part out of a rubber, screw-in chair slider, but it's rubber so it's not holding much...any ideas of which company might have made this or what it's actually called?

Thank you so much!