I just picked up some 1 1/2" PVC pipe fittings, and a 20w MR16 halogen flood at Home Depot. Initial tests leave me thinking that I may actually be able to see where I'm going with this thing!
I'll be building the light and attaching it to a front reflector mount this week (pics will be taken of the project) but I've not totally nailed down my power supply for it yet and I've still got to get some silicon to glue the bulb in and waterproof the leads.

One question I have is this: What about running the lights from 9v batteries? One battery seems to light it up fairly well, although I'm certain it's not 100% brightness, it may be adequate. Would two 9v batteries in parallel be able to run a 20w MR16 for a decent amount of time? (12v - not sure if they're made otherwise)
What if you over-volted it at 18v with two 9v cells? Would that destroy a 20w flood?