4-wheel Parts carries the Pro Comp Wheels, but you can order them through Summit Racing as well and usually have them in a few days from either source. I'm sure there's others that carry them, but 4WP and Summit are the big timers, so their prices will usually be less since they sell in higher volumes. Another benefit to ordering from these mail order powerhouses is that you can usually bundle a tire/wheel combo together and get the mounting/balancing done for cheap and shipped with a discount. All you have to do is bolt them on.
We just ordered a set for my little brother's '02 F150 4x4. He got them through 4WP online. $1420 shipped to his door for Four Black Pro Comp Series 52 Wheels in 16x8". Four Pro Comp 285/75/16 Radial Mud Terrains, and the Mounting/Balancing & Shipping all together. He literally unwrapped them and bolted them to the truck.