To answer my own question, I used Waters Tool and Hydro in Walland, TN. I'd highly HIGHLY recommend Mr. Waters, as he was extremely accommodating and did a great job taking care of the regs on my tanks. He met me near campus to pick-up the tanks, tested them the same day, and had them back to me that afternoon. Yes, an 8 hour turnaround time and he did a substantial amount of driving to coordinate the drop-off/pick-up. $35 per tank.
Also, this is the guy that Hiatt's Paintball refers their customers to if you'd like to hear another voice vouch for Mr. Waters.