If you want one that is not an office Disney one so it will be totally unique, check out Etsy.com. You can even have them make with your child's name on it. Or if you have lots of time on your hands, you can go to SnapFish or Mixbook etc and make your own. Mixbook lets you use clipart that you can find online to make each of the pages. I have seen people that have made a specific page for each character they want an autograph from to sign on using clipart. Here is a couple I have seen
Ordered ours from ebay. There is a seller there who makes awesome personalized ones (around $8.99 I think). Disney store online had them too but I liked that I could have my kiddos name on them.