I've long been looking for a properly sized messenger bag that can handle my DSLRs and 13" MacBook Pro. I find dimensions to be a critical point when looking at single strap bag, and many are too large, and some too small. When I saw that the Tenba DNA 13 was billed as being built around the devices I use specifically, I had to give it run. I'm happy to report that the dimensions are brilliant! I usually only run the laptop or the DSLRs for weight reasons, but I can fit all of it in there at one time. This is the only messenger bag I will keep around for the foreseeable future.
This is a fairly basic messenger bag that includes a removable padded camera insert. There are some features that could be improved, but as I move more to backpacks for EDC, this bag serves great in the grab and go role when just jumping in the car or when out afoot with the pram (a,k.a. buggy, stroller, etc.). The materials and construction appear good to and this bag looks like it will last.
If your kit is similar to mine, check these out at Amazon.
Carry on all and God bless you,