McMaster-Carr is one source, so is eBay 8020 Inc Garage Sale and there is at the least one other that will ship to your area if they have a store there but I can't remember the name. I think there was a thread over at Rocketry Planet.
The biggest cost for an 8' rail would be the shipping as anything over 6' IIRC comes by truck.
Depending on the weight of the rockets you are launching I would think the 10-10 (1" X 1")size works best up to 30 lbs. or so. Others will chime in on this.
Heh if you look at the description closely, it is an original 80/20 product, not a clone.
The only problem I have with Grainger is that I had to buy stuff using my work's account number. They don't seem to like direct sales to an individual. At least they let me pay and did not invoice my workplace.