curing and promoting coraline are two different things.
you can cure coralline with no light at all. just scrub off the dead soft material and wait for the ammo cycle to finish. some people dose kalkwasser and iodine, but i dont really see the point in that.
worry about the corraline when it is in the tank, with proper lighting and calcium levels, etc.
if you must put a light on the rock, you can get a swirly flourescent clip on from your local hardware store .