Plastic slides for aluminum windows

Hi, You could try glass shop like where they replace wind shield, cut plate glass, repair storm windows, etc.

That's not a bad idea. I bought some clear plastic L molding, I think it is used to keep people from scuffing the outside corners of plastic walls, especially children, especially in the kitchen. I was going to cut slides out of that, but haven't gotten around to it yet. Not sure exactly what the op wants, but this will fit pretty well for me.

My windows slide pretty well anyhow,

And it might also be possible to rearrange the window panes so that a different one is slid from in the previous 30 years. I say might because the weather stripping can be different on each pane. It might be easier to take a plastic slide from a good pane and put it on a pane that has to slide.