I got it at a place called "Little Dealer, Little Prices" that sells camper shells and RV stuff. I think it was about $7/ft. If you have a hard time finding some, I'd be happy to get some for you and ship it... I would imagine though that most camper places sell something similar.
As for the deadening question, I used 2 bulk packs of Dynamat Extreme, which comes out to 72ft^2, plus another 50 ft or so or eDead, which I don't really like. I just used the eDead on the inner panels of the doors, and Dynamat everywhere else. I didn't do the dash, but I did the floor up to the firewell, the entire rear wall, the sides by where the seatbelts go, and the doors inside and out. There are a lot of brands out there, and I'm sure there is stuff out there for cheaper that is just as good or better. The only reason I went with the Dynamat is because I was able to pick it up locally for really cheap. Square footage also depends on what you're putting it in and how many layers you wanna go. My entire floor is at least 2 layers thick, and 3 in some spots, and my outer door panels are 2-3 layers thick, and 2 layers on the rear wall. So you could get by with using less if you don't do multiple layers, but I figured I bought it, so what the hell //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif Needless to say, it sounds exponentially better than any non-deadened vehicle I've had. It punches me in the gut for sure.
Mike