My neighbors sons both work for Princess Rail Tours between Anchorage and Denali. The last time they were home visiting, we chatted about this exact subject. Both of them carry 44 Mag Ruger Blackhawks 300gr hard cast's and bear spray when fishing. When camping they will occasionally tote a 12ga shotgun loaded with Brenneke hardened slugs.
I don't see why that won't work just fine. With full 300 gr loads the .44 is a beast on both ends and while I like the .454 the .44 is not a BB gun.
And bear spray I'd take along just in case it's a bluff charge (a full charging bear runs as fast or faster than a horse so you won't have much time at all!)
And the 12 gauge shootie is best off all (and a lot cheaper than most pistols.)