Thanks all for your encouraging reviews!
The pattern can be found at
http://www.pbtex.com/html/chloebackpack.html (and it's free!). I modified it just a bit, making mine 2 inches shorter, since Kimberly is only 6.
No, there's no zipper. I put a bit of Velcro on the back of the flap. The pattern didn't discuss any kind of closure, and I thought it needed SOMEthing. I'm also searching for a big button, maybe yellow?, to put on the flap, just as a decoration.