Bear spray. Bring a chemical fire extingusher...
Bring a dog with you...
I would look through all of these fluffy calibers you list, find the heaviest flat nosed, solid bullet I could find, get it going as fast as I could, and pray a lot...
Please don't say 'bear' and 125 grain hollowpoint in the same sentence.
Hunting mountain lions, and stopping them, as with bear, are two different issues. Black bears are often run with dogs, as are mountain lions, and then shot out of trees, with a variety of marginal weapons, up to, and including, 22 short. A percise shot with a 22 short will give you 6" of penetration, getting a major artery, if you know what you are doing, and, the animal will hardly know it's been shot, which, is an advantage, since it will bleed out, without attacking you, or the dogs. Do I approve of this sort of hunting? NO, but, it's done.
Using a hunting example, when the person is discussing self-defense against a hungry animal, or a cat or mother bear, protecting her young, are really different situations.
They have tape somewhere of a mother cougar driving off an 800 pound brown bear, protecting her cubs. Something about lightning quick claws in the eyes, and nose did the trick.
Statistics show the most effective bear defense is pepper spray, bear pepper spray, and, it works very well against cats, and humans, as well. Handguns are NOT very effective against bears, or lions, in a defense situation. Rifles are, but, that's probably because the guy had the rifle ready, in a hunting situation, as the bear charged, or, the bear gave them a chance to get it out, like attacking a cabin.
finally, getting any of these guns to be reliable with heavy for caliber flat nose bullets is another problem. Stiffer springs, modified feed ramps, maybe necessary for reliability.
S