I would get in touch with Danny at DNCustoms.
You can search for him on facebook (dncustoms), check that page out to see some examples of his work or my buddy Dave's rotor is on here in pics and vids. They will paint almost any design/image/pattern you can think of onto your rotor. He won't tell us what paint he uses, but I don't think it's airbrushed on. They have an artist paint them by hand.
If you only wanted it painted white, I'm sure he'll do a decent price. The average for artwork is £35 but very much worth it imo...