If you don't have time to process each file in RAW and want to get it right in camera,
ExpoDiscs work very well. It hangs on a strap around your neck, or just put it in your pocket. Put your AF into manual, shoot at your light source with the ExpoDisc in front of the lens (like any filter), select WB and the results are great! I just bought one down at SepCon and I'm very impressed. Good luck!
Steve Fogarty