Just order and get this one from Dealextreme.com at only US$3.95 shipped. They have white and blue color.
http://www.dealextreme.com/details.dx/sku.26822
The light is evenly distributed, no hotspot at all! It has only one bright LED, feeded by 2*CR2032 batteries (included). Not sure how many hours before you have to replace the batteries.
Just clip it at front cover which is folded behind your Nook. The clip is bendable and stay put.