I buy from all over, but mostly local shops. Eastside Records in Tempe has by far the best selection of used LP's I've ever seen. Zia Records has four locations in Phoenix (as well as two each in Tucson and Las Vegas). The relocated and expanded store in Phoenix had some great used vinyl put out for the re-opening. While still technically independent, Zia seems to be growing into a chain, at least locally. I also buy new and used stuff from Amazon, sometimes ebay. If I can't find it anywhere else, I'll pay the list prices that Acoustic Sounds, Music Direct and Elusive Disc charge.