I guess the obvious answer wouldbe a KL4 but everybody does that /ubbthreads/images/graemlins/smile.gif It would be cool to use an "E" to "C" adaptor, and put something like a KT1-HA on there. I like turbo heads and really like the Vital Gear bodies too.
Hmmmmmmmmmmmmmm An Aleph 3 head and whatever 3.7v bulb will fit (I have NO experience with Alephs).
Personally I'd probably try to make an adapter so I could use my 3.7v E2e bulb in it, with a Pila 168S. I bet the Aleph 3 head would make for a great throwing light.