I have a Think Tank Urban Disguise and love it. The one that also holds a 17" lap top
It looks like a brief case, so it doesn't stand out. Well padded with many pockets for batteries, filters, etc. You can get back pack straps for it. I have them -- the thing doesn't carry as nice as a backpack but the back pack straps come in handy when my hands are full.
Enjoying life one moment at a time.