Made by Rae's Toddler Backpack. I've made it, I think, 6 times now and I still love it. It is easy to put your own twist on it because it is such a nicely done pattern. One add on was the front pocket. I was really winging it on this part and though I'd do some things different if I did it again, I love the way it looks.
To give it maximum structure, but still have the ability to sew it with out pulling my hair out, I used Pellon Decor Bond on all of the main pieces including the lining. I actually use it in most of the bags I make. (Smaller bags only need a single layer. )
I wanted the back to be more comfortable for her when she wore it so just before I put it all together, I tacked in pieces of Annie's Soft and Stable. I ended up putting it in the back, front and bottom. It is extremely easy to sew, and gives more structure without much extra weight. Have you used this product? I've done a few things with it and I love it.