I have a messenger bag that I use to carry my laptop around, and also just various other useful things (like pens and notepad when I'm at a convention or such). It's incredibly plain. I wouldn't mind getting a bit more "nerdy" bag. And thankfully, Steve Jackson Games is here to help. They've got a Munchkin messenger bag. And until December 15th, they have a special deal going with it.
When you order a bag from their webshop (aka - Warehouse 23), they'll throw in a free Munchkin game and expansion set. Who doesn't love to get free games? I know I'm rather partial to them. I'm sure you would like them, too.