The S&W Model 500 comes in a 4" version that would be a great pack gun. I'd load it up with a 350-400 grain solid bullet. .50cal is a more than big enough hole, and penetration would be outstanding. The recoil is stout, but not unmanageable as long as you're committed to practicing enough with it to be proficient. The only downside to the Model 500 is the high cost, but if it were me I'd look for one used before I'd buy one new.

The SRH Alaskan would also be a decent choice (I'd choose .454 Casull over the .480 Ruger, but that's just a matter of preference), but I think the 2.5" barrel is excessively short. I'f they'd made it a 4 or 4.5" barrel it'd be better. The gun is for back country defense against nasty 4-legged critters and can be carried in a manner suitable for such, not a CCW revolver to be carried in a front pants pocket during a midnight trip to the convienience store, so the 2.5" barrel is unnecessarily short and compromises performance and handling a little too much IMO.

Mike