We are talking about black bears, right? I've had 5 or so black bear encounters including one sniffing me while sleeping under my tarp, two on bike rides, one while hiking, two on the side of the road (we got out to take pictures). In all cases, it was hard to keep from spooking them into a mad dash into the woods. It's never crossed my mind to arm myself against a black bear. A dollar store air horn, or a whistle would freak one completely out.
A trash can hibuated bear might be another story but even those are easily scared away.