Several months ago I made a few messenger style bags and sold a couple online and a few more at craft shows. They were a little different, I had not put a zipper in those and they had a flap closure. Here are a couple examples:
This new one has a zipper closure and a back pocket. I made a tutorial for the new one and have listed it in my Etsy shop and it is called The Li'l Lizzy Hipster and you can find it here.