Like JWR said, get a 12 ga. Yes, it would be nice to have a good revolver. If .357, get a GP-100 fixed sighted 4 inch without the underlug (saves weight and can be broken down in the field to pieces for cleaning) and get some 180 gr sledgehammer hardcast loads (I think Federal makes some like that). The GP is only if you screw up and either drop your shotgun or it is out of reach. The shotgun can use any 12 ga. slug on bear and it will do (one of the reasons I like the shotgun, ammo selection is not critical as long as it is buckshot or slugs, we are talking short range bear defense, not hunting).
Look at it this way, no .44 mag, .45 super, even .454 magnum can even approach the power of a 12 guage slug. 400 plus grains at 1600 fps ought to do it.
Any good make pump (might want to get stainless steel if you are as lazy as I am) will do. I use a Winchester 12ga 1200 stainless Police model with Tac star side saddle. When hiking 6 in the magazine, 6 on the sidesaddle. A Ruger Speed Six on my hip. Not expensive. The Winchester I bought at a pawnshop for $190, the Ruger also at a pawn shop for $225. Both stainless. I have used the 1200 in shotgun schools (basic and advanced) with not one jam, malfunction. Worked evertime. The Speed Six I use in IDPA. Never any problem with it.
Yes, I have other guns, but these two I guess I use the most now when in the sticks. They are simple to use, powerful, easy to clean, and not expensive (yes, that is important as lots of people would leave their prized gun back at camp, these two I can drop in mud and I won't cry over it).
Hope that helps.
Deaf Smith