Unfortunately, that lamp/lens is not something thats available on its own as fr as I know. I can tell you what I did on mine though!
The lens I used is actually a cut 7/8" test tube. It fits perfectly in the brow piece and is bonded in place on the backside with window-weld. The lamp is something you'll have to choose yourself though, any bulb/holder that fits will work, its all up to you how you want to mount it to the bucket so the bulb is replacable if it burns out, and the mount area is sealed to prevent water from entering the bucket.