This is the only good site ive found http://www.straightlinerails.com/. . but its pretty expensive. . and im not skilled in the art of wellding so making my own is not an option. I would prefer not to have to make a PVC-pipe rail
Do like I did. Contact a railroad-company or something, and get some railroadtracks. I got two straight rails at home now. Kinda hard to bend though, and heavy as hell! But they are sweet, and I got them for free.