I've finally pulled everything together for my 20-watt, 12-volt light and here are the specs:
Housing: Nite Hawk Nomad
Bulb: Currently a Philips 20W/12V MR11 bulb with an unknown beam angle. I have a BatterySpace 20W/12V MR11C bulb with a 12º spotlight beam angle just in case.
Mount: Nite Hawk One Touch Universal Handlebar Mount
Battery: BatterySpace 12V 3500mAh Laptop NIMH Universal External Battery
Connector: 5.5 x 2.5 mm
Battery Bag: Nite Hawk Nomad
I can't wait to get out and see how well this works.