They were so notorious for catching fire, I really don't think you're going to find any floating around extra. (my son's caught fire, too)

I can order them from my Apple store for $80. There are a couple other companies making chargers (which their websites say don't catch fire). I can't remember what they are, but I found them by googling "iBook charger".

Right now I'm in the situation of needing a new battery for my iBook, later I'll be looking for a new charger because mine is worrying me a bit.