I also use a messenger bag for my gear, a Timbuk2. I use it with a Domke insert. If you do a search for Timbuk2 and Domke you will see quite a few examples of people using that.
I liked the Urban Disguise idea, but as someone else said, no flap, just a zippered opening, and I'm not even sure if its a water-resistant zipper that is used.
I liked the Urban Disguise idea, but as someone else said, no flap, just a zippered opening, and I'm not even sure if its a water-resistant zipper that is used.