Window roller Product Code: 87-036

Hi I have an older house w/ Nylon sliding windows. Only markings are "SERIES 2500" on the window latches. The window rollers are worn out. Here is a link for what appears to be the current roller's :

I would like to replace them w/ brass or steel rollers - wheels alone or complate assembly. What do I need ? Thanks.

Here are a few pictures. The roller assembly measures 1 1/2" long, 9/16" wide, 1/2" tall w/ 1/2" roller wheels.