~1/4 inch nylon buttons to cushion slides of general aluminum 4400 series single-hung windows

A window pro recently replaced the glass in one of these windows. In the process, he lost the four little nylon dome-shaped buttons that were attached to the inside face of the moveable part of the single hung frame, cushioning between the moving frame and the fixed one. They were apparently friction fit into receiver holes in the frame. These buttons prevent direct contact between the aluminum of the sliding part of the frame and that of the fixed frame, thereby aiding the slide and preventing aluminum/aluminum binding and wear. I learned from the current operator of "General Aluminum" that my windows pre-date their takeover of the GA company in the year 2000, so they can't help me with parts. Ideas?

87-132 does indeed appear to be the exact solution! Before ordering, I will need to confirm the 3/16 shaft size matches the holes in the window, but am quite optimistic that it does based on the MK-I eyeball that I have been using to measure until now. Thanks very much!