Pretty much any of the LED types will work, there are several manufacturers that offer them.
I'm not much of a moonlight fan, however. They most likely don't do anything beneficial for the coral or fish, are yet another item to trash up the electric cord tangle, and IMO don't look all that great.
There is also a thread in the SPS forum where people have gotten interesting results by turning off the moonlights and letting the corals just have darkness at night. They claimed to have better polyp extension and even growth. I don't know for sure that it's that big of a deal, but there isn't any proof that the "moonies" do any good either.
For a 90, Current USA makes a nice LED called, I think, the Powerbright. If I were going to rig up a 90, that's what I'd use. I would use the whites since moonlight isn't blue.... unless it's due to some freakish air pollution that I've never seen, lol.