I can't help with where to go. But if your cylinder will be hidden, there's not much reason IMO to buy a pretty new aluminum job. In addition, many or most places seem to do swaps rather than refills, so you'd be limited to places that will refill, and many of them don't have immediate refill service (you might have to wait a few minutes, a couple hours, or a day or two, depending on how they work).
But, 1)if you can get a good deal on an attractive cylinder, and there's a place 2)nearby, 3)that does inexpensive refills, 4)while you wait, then go for it. I know of 3 places offhand in town down here that do swaps, one of which is half the price of the other two. And I know of no places that do refills (I'm sure they exist, but haven't found any).
So your first step is to start making calls and asking whether they do swaps or refills, and what their prices are for 5, 10, and 20# cylinders. Some of them won't do swaps for the smaller cylinders. Google welding supply stores (there's usually an AirGas around), fire equipment, gas supply, etc.
Hopefully you'll get some responses from local folks who can save you the trouble of making calls