I deliver skid steer parts to a powder coat shop. They coat all kinds of industrial parts, including wheels for case/new holland skid steers. Very durable and a nice finish. It isn't very expensive either. Maybe $20-$40 per
Shoot me your email and I'll shoot you a pic of my painted rims. If you're careful with your preparation, they can be painted at home and hold up very nicely. The key is a good quality clear-coat to help resist brake dust and road grime.
Powder coating is even more durable, but much more expensive. One word of caution - if the car is gonna be tracked, and hard brake usage is anticipated (road course/autocross work), DO NOT have them powder coated in the area where the lug nut actually touches the wheel. When brake temps are extremely high, hub and wheel temps get high too. Powder coating is only good to somewhere in the 300-350F range, and high temps in these areas can melt it right off causing your lug nuts to suddenly be loose - like right in the middle of braking from 130mph for turn 1 at Texas World Speedway. Don't ask how I know....