I know you're looking for something smaller, but depending on your job a messenger bag could be just the thing.

My best bet is either a backpack or messenger bag. Now that I have a laptop as part of my EDC, a messenger bag with padded laptop section is ideal-- and leaves plenty of room to carry my contingency gear.

When I'm taking classes, I fit in (though as an older student / professional). When I'm working in IT, I come off as a slightly geeky professional. Either way, I fit in, look professional, have plenty of freedom of movement, and can carry the gear I need.

The trick is to avoid over-packing with all that space I have. A half-empty bag is NOT a problem.