There are plenty of welding supply shops in the area. I don't get mine filled in Charleston, but you will see plenty of ads in the phone book. Look under 'gas-industrial' or 'welding supplies'. Since the Charleston area is quite spread out, you will probably find quite a few in other towns that are within travel distance.
I get mine in Beckley at Beckley Welding. Last time it was $15.00 for a 10 lb. fill in my tank.