Give some consideration to The North Face Mountain Lumbar Pack. ~365cu. in. inside storage. You can comfortably wear it on your waist, you can add shoulder "strapettes" from other manufacturers, or ( by buckleing the waist belt) wear it on your one shoulder or even slung overhead and one shoulder, like a sling bag. The built in water bottle pockets are very secure. I've attached another small belt type pouch, to the built in straps that let you carry a shell. If you shoulder it, you can also attach a cellphone or other yoke type pocket. Finally, you can slide a multitool/flashlight holster onto the waist belt. Believe it or not, based upon my own experience, its very versatile, non-tactical and low profile, even in NYC, especially in black.