So I was in my local dollar store the other day and I happened across this cheap junky book light. I've never bought a book light before because I'm too cheap, so this one appealed to me. And to be honest, I know I'm going to lose it, break it, or the batteries will run out just when I want to use it most.
This one only cost a buck, and it's powered by 3 button batteries. It works okay, and if I ever need to replace it I have a second one still in the plastic.
I checked on Amazon, and the cheapest one I could find started at about $4. I think I got a good deal.