Like Ironbender asked "backup for what?" Will you be hunting, fishing, sightseeing, or what? If you will be rifle hunting, why do you need a handgun backup? Even a .30-30 rifle is more powerful than a .357 pistol.
Don't get me wrong, I often carry a pistol while I'm hunting. I currently have two .357 mag pistols and two .44 mag pistols. I have only hunted in Alaska once. It was a DIY caribou hunt some friends and I did on the peninsula, SW of King Salmon. I carried my .44 mag Super Blackhawk. I didn't need it, but I just wanted to carry it.
Years ago, when I lived in NW Montana a friend and I were fishing in the back country. We both carried pistols, he a .357 and I my .44 Ruger. When we stopped for lunch, we decided to do some plinking at saucer sized rocks. His .357 would knock the rocks down, maybe breaking them in half. My .44 mag would shatter the rocks into gravel.
In 34 years of hunting the Montana back country, the only grizzly encounter that I've had was one year near West Yellowstone. We were camped at the end of a road, and we had a moose and two elk hanging in the stock rack in the back of my truck. One night I went outside to check the horses, etc. just before turning in and a 300 lb grizzly 10 yds above me on the bank started to snap his teeth at me. I had the lantern and was carrying my .44 Ruger. I fired one shot in the air over his head. No reaction. I fired another shot into the tree next to him. Again, no reaction. So I picked up a tennis ball sized rock, threw it and hit him. He ran off and we never saw him again.
I've killed a couple of balck bears with pistols. Both were one shot kills, but the bears were not charging. To kill a charging bear, I would want as much firepower as I could get...and you have to be cool enough to shoot it accurately. I guess a .357 would be better than nothing.
