I bought this one from Amazon
http://www.amazon.com/gp/product/B00...895863-5939951
I've only had it for a little while but the things I like about it are :
Nice bright light when on highest setting (there are two settings.)
The bulb is just a little shorter than the width of the reader screen so it lights the screen evenly across.
Once it's positioned well it casts a pretty even light across the whole screen, just a little drop off at the bottom of the screen.
If you use rechargeable batteries, it comes with a cable that lets your recharge them via USB.
The price is pretty good.
Once I've used it for a little longer I'll post back a my experiences.
Rob