I have used the Radio Shack 273-1776 12V 1 amp Power Adapter many times for many applications over the years.
Although I cannot say for the iLiad, for the Sony Reader I also have used an iGo Juice (also from Radio Shack or
www.igo.com) that will work with wall outlets, car adapters, and airplane power adapters. For the Reader you need plug (iTip) A54. Works like a champ.