AK_Skeeter
WKR
Bear spray can be purchased locally in Alaska and and taped outside of the plane with duck tape on the strut of the bush plane. Best to check with the air transporter while planning the trip.Bear spray can be tough to fly with in Alaska, so when often effective on camp bears, it's not always an option.
And having argued with brown, grizz and black bears over carcasses and camps, I can and do take a rifle or 12 ga over a handgun. And yes, I've done multiple range days shooting at those "charging bear" targets. Shot a few of those real bears too for that matter.
But I also don't sweat the caliber thing for bears when I'm hunting other things. Remember that non-residents can't shoot grizzly without a guide, and state law doesn't extend "defense of life and property" to game meat. For the average NR hunter without a grizz tag, your one and only option is usually to back off.
Worry about the rest of the logistics. Take whichever gun makes you happy. The caribou won't know the difference. Virtually everything else about the trip will be more important.