I have a neighbor who hunts in Alaska quite often, he carries a stainess 5.5" Ruger Vaquaro in 44 mag as a backup. Though he primariy uses a rifle, he has taken caribu, black bear, mule deer, white tail, antelope, woverine, and other stuff with it. He says is more user friendly and lighter than the S&W 629 he used to carry.
For a primary pack weapon he suggests a long barrel 44 or other large magnum revolver with or without a scope and carried with a sling. The nice thing about the 44 mag is that you can load anthing from heavy magnum loads, 44 specials, light plinking rounds to shot cartridges in it.
I have a 7.5" Stainless Ruger Redhawk I carry on my ATV when working on my 54 acres in Northern Michigan. We have bears and other criters, though the bears are pretty skittish and I have no desire to shoot one. I used to carry a shotgun but a pistol is much more covienant, the holster just straps to the handle bars or front rack.
BTW, the neighbor used to hunt cats with his 44 using a round lead ball over just a couple grains of powder. About 500-600 FPS. Those cats looked like they were hit with a bowling ball, or so he tells me.
Another option is a single shot Thompson Contender in whatever caliber.