i bought:
http://www.amazon.com/gp/product/B001LRPN0S
and it works GREAT! i, too, like to read a LOT and had the ereader 'die' on me because it ran out of charge mid book. so i charge it up using that wall charger inbetween times i dock it to 'puter when loading/unloading library books.
hth.