AngryBird: I got into my Yellow Pages and looked up Sandblasting and Powdercoating. Both businesses do sandblasting, and can do the job. I just called all of the shops in my area and took the cheapest deal offered. The sandblasting shop I used quoted me $25 over the phone, blasted my drum while I waited in the parking lot, but charged me only $20 because it only took him about 10 minutes to do.
Most shops wanted to quote me their hourly rate and try to figure it out from there. I got estimates running anywhere from $40 - $75. The shop I used was a small father and son operation (with mom answering phones,) and they treated me right. I'll remember them when I need something else done.
Good luck!