Make sure you stress the fact that in no way do you want the coating to dull the finish, call a few shops, and ask to see examples, the guy local to me actually clear coated his set of polished torq thrusts, and you could see them on the vehicle, that and he had a huge sample area in the office to see various finishes he offers.

 

Here are some links about powder coating:
http://www.finishing.com/Library/pennisi/powder.html
http://www.ppg.com/car_indcoat/powder.htm

And, it seems that there is a powder clear coat (learn something new everyday):
http://www.ppg.com/car_indcoat/powdernews1.htm

 

Intro offers clear powder coating on their wheels, maybe look to them for help in who can do it.