Perhaps this might help someone else. A little research and limited experience so far I got the following info. It might help if others can add to it so we can build a good info base for air/nitrox fills.
Myrtle Beach, SC area
Coastal Scuba - pre-blended nitrox, no O2 clean system
Express Water Sports - pre-blended nitrox, no O2 clean system
Nu Horizons Dive and Travel - pre-blended and partial blend nitrox, O2 clean system
Charlotte, NC area
Divers Supply - partial blend, O2 clean system
Myrtle Beach, SC area
Coastal Scuba - pre-blended nitrox, no O2 clean system
Express Water Sports - pre-blended nitrox, no O2 clean system
Nu Horizons Dive and Travel - pre-blended and partial blend nitrox, O2 clean system
Charlotte, NC area
Divers Supply - partial blend, O2 clean system