when in rome.
if briefcases are common in your area of work, then a "tatical" briefcase will blend in (as oppossed to the horrid and ugly fannypack). Imagine a fannypack worn with a suit. ugh!
That would not blend in.
In college towns or hip metro type of communities you'll see a lot of backpacks and messenger bags, or as I call them: Murses (short for "man purse". You could make those "tatical:" as well.
A zippered Franklin planner can be made tatical and they make planner holsters. Those would blend in seamlessly in the business world.
So basically I guess you have to do a "when in rome" type of thing when concealing your weapon. Just keep your awarensss about you. Whatever route you choose can work if you training supports it.