There might be something just for this but I would take a look a laptop backpacks they usually have lots of compartments with padding.
I know you can take some great pictures with and SLR. But why don't you use a smaller camera. I have some really cool pictures that I have taken with my old Nikon S4 and My new Olympus 850SW. The Olympus also happens to be Shock & Water Proof. Check out there web site for others.
I have two friends that are professional photographers and were amazed the a few pictures I took where off of point and shot cameras. Not that I'm saying I know what I'm doing, I'm sure I just got lucky, but that you can get some good pictures off small cameras too.
Or try
Google