It charges via a mini USB cable so all you need is an AC adapter for USB. I use the AC adapter for my iPod and it works fine. Something like this.
http://www.nextag.com/Cables-Unlimit...92/prices-html
You can buy a spare battery for the Cybook from Bookeen. I received a spare with the deluxe package and changed the battery once. It's a very fine screw and I almost lost it. I wouldn't want to try changing the battery on a hiking trip.
You might want to consider something like this that would allow you to charge via an external battery. I haven't tried it though.
http://www.modernoutpost.com/gear/de...r_uno_slim.php