I have a M-Edge e-Luminator Kindle Booklight for those times when I use a book light and it works really well with my Oberon Kindle 2 and Kindle 3 covers. The one I have is currently out of stock, and Amazon doesn't know when they will be available. However,
this one, which appears identical in the photograph as far as I can tell to mine, is in stock, and I imagine would do the job just as well. A big plus is that it only uses one AAA cell for power, thus greatly reducing the overall weight.