Here is my landing light. It is a Whelen Parmetheus PAR-46 LED light. It is very bright! I made the housing from fiberglass. For the mold, I used a glass vase about 6 inches in diameter and about 12 inches tall that I found at a Michael's craft store. Even though I waxed it before laying up the fiberglass, I must not have done it right, because I still needed to break the vase to get it out after the fiberglass had cured. (It was a real pain, too!)
Once the housing was done, I cut a hole in the front of the cowling of the approximate size and shape (but slightly oversized). Then I temporarily mounted the light to the housing using some silicone, then wheeled the plane out into the street at night to aim it. I picked a mailbox about 200 feet down the street to aim for. When I was satisfied with the aiming, I used some 5-minute epoxy to temporarily hold the housing in place, and then reinforced the whole thing with more fiberglass from the inside. Once cowling is finished (and painted), I will mount the light to the housing permanently with silicone.
Total Time: 19.5 hrs.