This site has a lot of Yorkie pictures that can be put on a grocery bag, and that bag looks to me like a good one for carrying books.
Yorkshire Terrier
This site has book bags. You could get a plain one and have a Yorkie embroidered on it. I bought the girls a canvas duffle bag and had their names and a Yorkie embroidered on it.
Dog Groucho Quote Book Bag from Zazzle.com