I've been trying to get around to making a pattern for my messenger bag, I will one day Becki I promise. This bag by, Claire (AKA bouncyflea) over at Craftster, just looks like spring. So until I get my pattern made you might want to give this one a go.
Here's her tutorial. I haven't made one yet myself yet but her instructions are very clear and it looks quick to make - my kind of project. Thanks for generously sharing it with the rest of us Claire.