Anybody know where to get cheap plastic window track for plexiglass for sliders or maybe how to make some? I bought some a few years ago made by Stanley but can't find them anymore. Thanks in advance.

Try McMaster Carr. I know they have aluminum ones pretty cheap that I used on my blinds.

I use this stuff sold at McCoys called P38 Millet Aluminum. Looks like a small case h from the side profile. It was like $4 per 8 ft. I think its true purpose is to be used on siding to link sheets together. Works great. I have used it with 1/4" plexiglass for 3 blinds. It comes in 7/16" channel and 1/2" channel.

I use the same material from mccoys, but put felt liner in it to hold window in place.

I see you mentioned cheap. For bottom channel use 1x4 shiplap or cut the groove with a router out of old privacy fence, cut 1/4 or so wide and 1/2 in deep. For top groove or channel, put a lattice board or 1/4 inch trim board on part of the 1/4 or privacy fence board. Leave enough height play where you can lift the window 3/4 inch from bottom and remove or replace the window. With router you can also route 1/2 of the fence board to get the same result. This won't work if you want the whole side to be a window. I like 1 foot wide windows the I can partially open. Then I can also make a whole deer blind fairly cheap out of privacy fence.

I used aluminum channel from Home depot.

Lowes and Home Depot have a plastic U shaped plastic channel, that allows for easy sliding for horizontal windows. It is used for holding lattice.