Are you looking to buy over the counter products or are you going to be ordering online? By purchasing online, you will be able to select from a larger selection of product lines that aren't sold at big box stores or auto parts stores.
Do you have any paint and body shops in your area? They usually carry some professional lines of detailing products.
AutoGeek.net carries a lot of different high quality supplies and their prices are some of the best around. They price match, too, if you find it cheaper somewhere else.