Yes, autograph books are at mainly every shop in WDW. Including hotels, parks, Downtown Disney. So are pens, but I suggest if you don't want to spend money than you bring your own. They are around $5.99-$7.99 from what I can remember. I forgot mine at my hotel and I bought one. When you enter the parks check at the booths and shops. Or when you get to your hotel buy one there. Though, it would be cheaper to make one for yourself. I had never thought about doing that.
Thanks for the great idea!
Azure