Hey Lee,
I got them at home depot.
They come as barn door sliders, they were pretty over rated for this @ 250 lbs per wheel for a total of 1000 lbs capacity.
The canopy weighs about 300 lbs (even being total aluminum) with all the ballasts mounted on it, But all others i looked at seemed not enouph, wich included pocket door stuff and any cabinet type tracking i could find.
The result was about a couple hundred more than pocket door sliders to get it hung, but now i have one that i can ride on too.
If your canopy was about 100 lbs or under, i would definatly look at some good pocket door hardware first.
Marc.