I use a LowePro Zoom 100 AW
. It comes with both a shoulder strap and backpack style straps. When I'm carrying a backpack, like on a day hike, I wear the Zoom 100 with the backpack straps - but I wear it backwards so it hangs on my chest (also good for skiing). The 100 will take a pretty long lens, I use it with a D2x and 70-200 AFS VR
lens. But if your lens is shorter you could go with the 70 AW
One caution if you go with a tank bag. Mine has big magnets that help hold it on, and there could be a risk of those magnets damaging either the camera's memory or photo's on the chip. It hasn't happened to me, but I always keep the camera in a camera bag when it's in the tank bag. There are tank bags out there with no magnets, but they're tedious to clip/unclip.
Have a great trip!