Check restaurant suppliers as well. You can get used tanks for less as well. If it is going to sit out of site some dings and scratches can save you some $$. The inside is still going to be shiny and new.
I bought mine at a welding supply store called Airgas. A 20 pound tank filled was $84. Also, there is not much point in spending money on a brand new shiney tank. You'll end up exchanging it when it is empty for a used tank. Most places send the tanks out to get them filled, much like the gas for your bbq. Unless you can find a place that actually fills the tank while you wait, you might as well get a used tank and save some cash.