Make it a rifle if you are serious about bear defense.
If you want to buy a handgun or shotgun and want a reason, that's another matter. But for serious bear defense, ditto to Rainshadow and others about a handgun. You have to be really good. Also, compare the impact power (energy at the muzzle for example) of a 44 mag pistol with a 30-30 carbine. Even big handguns are pretty puny.
As to shotguns, none of the few guides I know who go after big bears think much of shotguns as bear defense, with any size shot or slugs. I have carried a 12 gauge with 00 buck for grizzly, and after talking to those guys, I am very glad that I never had to use it. As further loss of confidence in buckshot, I shot a small blacktail deer with 00 buck. The minimal damage and penetration was amazing compared to what I expected. The second shot was a finisher at about 2 feet range into the neck just below the ear. I expected it to half sever the neck but it merely mussed some hair and the buck still struggled for a few seconds. I had to brush the hair back to see the entry wound. It looked like someone had jabbed the deer with a #2 pencil several times in a tight cluster. Inside, the shot did not even break his spine and did not penetrate on through. This was a little chicken necked fork horn.
A shot in the face with smaller shot might blind a big bear and discourage him. Might, depending on range, size of pattern, coolness of shooter, etc. In a real showdown with a big bear, the best repellant is a big diameter rifle bullet. A short, handy rifle is the best tool to deliver it. Those heavy guide guns in stainless sound good, or a cut down bolt rifle. There is no comparison between a handgun or shotgun and a big rifle in terms of power, penetration and damage to the critter.
Buy a rifle and swap it for something else when you get back.
However, a rifle isn't very quick unless you have it in your hands. Gary Shelton, the bear expert from Bella Coola who trains salmon stream workers in bear defense, wrote that many people could not get off a shot at a cardboard "bear" that charged them. (My memory may be off a little on the exact distance but I think it is 15 yards. He has them wading and the bear comes out of the streamside brush on a wire.) If you are in lots of bears, one member of the crew with rifle in hands might be cost effective.