McMaster Carr has the rail, I think it was about $20 for a 6' length of rail. Good stuuf. Matt Stums web site's FAQ section lists come sources. McMaster Carr sells the 80/20 rail.
I think if you do a search on the forum for launch rail you will be able to find the exact McMaster Carr part number.
I use the rail and Matt's buttons and would never go back to rods and lugs.