Here's a thought....
Why not make your own track out of pipe or box tubing?
I'm envisioning say 3"-4" rectangle tubing or pipe cut longer than the length you need for a track. Clamp a straight edge to it for a guide so you can cut a nice 1/2" slot out with your cutting torch, or plasma cutter. Make the track pipe longer than needed so your don't have to cut clear to the ends.
Before you cut, pre-drill holes every 16" or so (above where your internal rollers would run), and install a bolt and nut on the 32" holes so when you cut, it can't warp out of shape. Then use the other holes to lag screw or bolt onto your building.
You could fabricate rollers with 5/16" diameter eye bolts, and the appropriate sized wheels that fit inside the pipe, bolted to each side of the eye bolt.
Maybe pre made track and hangers are cheaper than this. I don't know as I've never bought them.