Actually just thinking about it I'd definitely take my 30/06 after one, if he went down in thick cover that wouldn't be a problem as I'd be hunting with a guide.
He would earn his pay going in after it while I sat outside and waited for the all clear.

But back on topic, in what situation would you need a handgun for bear defence?
As near as I could figure I'd only have one around camp or if I was fishing ect.
Any time I was hunting you would presumably have a rifle with you, and even a 308win will out perform any handgun out there.