THIS SITE has HID projector kits that fit our 7 inch light buckets. Can't comment on how good they are. Stick with a projector kit instead of an HID bulb alone. Our stock buckets may not handle the light output of the bulb.
My chum installed an HID bulb in his stock metric cruiser headlight and was constantly flashed by oncoming traffic even on low beam. He pulled it and went back to a good quality Halogen.