I just use one of those standard clip on work lights that you can get at any hardware store and put in a screw in CFL. I then mounted an L bracket on the back of the stand, and clip the light to it. It has worked extremely well for growing chaeto. My chaeto has increased in size by about 5X in 3 or so months.
Here it is mounted over the sump in the stand:
Granted, I am running a 20gal for a sump... so you might need a slightly larger lamp than I have, but I think I bought the smallest variety available. They come in larger sizes. It all depends on the size of your fuge area though.
Anyway, I am sure there are slicker looking fixtures out there, but at about $5 bucks, it has worked like a champ. If only the rest of the build had been that cheap