Write one yourself! I wrote many, many books for my kids when they were little. I could make them laugh because I knew what they thought was funny, and teach them things that other age appropriate books were not teaching them!
It doesn't even have to be anything elaborate! I always did mine on construction paper. The pages were 1/4 in size, and I stapled them together for the binding.
If you want to get a little more fancy, write the book on your computer, and upload (with clipart) to lulu.com. You can even have a cover of your choosing and everything. (You can draw a baby on Holly's belly and have the other kids stand next to her. Then have that for the cover!)
This is really fun to do! They can make it an event! :)