I am still shopping for glass track for a cage I’m working on, it is 47 inches wide across the front. I bought the el cheapo plastic track, but still not sure that’s what I’ll end up installing. Figured I’d share some of these choices and sources and hope for some input here.
Rockler Woodworking and Hardware
4 foot plastic sliding door track – The cheapest type- $16.49 upper and lower.

http://www.rockler.com/product.cfm?page=2275&filter=plastic%20track
Cabinet Ware
Complete ball bearing type, they have a .pdf file you can open.
http://www.cabinetware.com/Track.asp
Woodworker’s Supply
Three and four foot long assemblies

http://woodworker.com/cgi-bin/FULLPRES.exe?PARTNUM=939-882&LARGEVIEW=ON
Boat Owner’s Warehouse
Nice stainless steel track with little felt cushion and little brush type glides, very interesting. Might be hard to clean the you know what out of it.

This site also has a white plastic track for boats that looks like it fits really tight, like water resistant for a boat window.

http://www.boatownerswarehouse.com/browse.cfm/4,8698.html

