sliding window glass rollers

I have to replace some plastic rollers for aluminum horizontal glass single pane windows made by international in 1976. The roller assembly is 5/8" deep, by 2" high, and about 1/4" thick.(They slide into the slot that is 5/8"x 1/4" from the bottom and held in place with a screw going through the open end of the slot on the window edge. The roller itself is about 1/8" thick by 5/8" diameter.

Any help you can give would be appreciated. Thank you.