I've put together a light fixture for the loft. It'll bolt into one of the rafters, and should provide enough light for reading.
I used a piece of aluminum pipe I had laying around that was just the right diameter for the bulb and base. It was a bit of a tight fit, but I eventually figured out how to cram everything in there.
With the light switched on, it draws about 200 milliamps. The over-sized battery I have should give me close to 200 hours of continuous light!
I'm planning another fixture for the kitchen. I'll put the switch on the wall instead of in the fixture, which should simplify things.