Yeah, the one that I used for my wheels isn't just on the South Shore, but it's on the Cape! They're in Borne, just over the bridge, and were VERY reasonable and the owner, Bob, was a great dude to deal with. Here's the
site.
I was looking into a place in Merrimack, NH called Extreme Powdercoating. Similarly priced, and the guy was cool on the phone. I didn't go with them pretty much because of my [sometimes silly] stick-with-family-business-in-MA rule.