If you unscrew the Vistalite battery packaging, you will probably find a standard battery pack, available from any electronics store for $20-30. In my system, I just use one of those cells in my own packaging (an old waterbottle).
I can remove the bottle to prevent theft, but I leave the lamp unit (a dynamo lamp) screwed onto the forks. One dissadvantage of flashy commercial lighting is that it is expensive, attractive and easy to remove. I suppose you could remove it every time you stop (along with your seatpost and front wheel), but for a utility bike, that is so much a waste of time.