What kind of budget do you have to work with?
Many racers and Packs prefer using a BestTrack, but there are other options as well.
http://www.besttrack.com/
Prices for a 3 lane 35' track would start at $765.00 shipped to your location....
It's possible you'll find someone who is looking to sell their used track, but typically assembled tracks are not ship-able except at great expense.... Ideally you want to find someone local if you are going for a used track, that can be a challenge....