This argument always seems to go to one extreme or the other...with niether side typically have first hand, in field evidence to support their opinion, just stories or articles pointing one way or the other.
As most folks that get into these debates, I've never had to shoot a charging bear or even been close enough to one to have concern so take this purely acedemic opinion. After much reading and discussion over last few years my take is this:
If you feel comfortable carrying 9mm in griz country for defense and having that pistol gives you the peace of mind to enjoy your time there more without feeling like your being hunted or in constant danger...then go for it.
Same with the 10mm, .44, .454, .460 or .500
Proper shot placement with any will do the trick if need be.
The specifics of the scenario will dictate how it all works out. In some instances it doesn't matter what your carrying, you may not even get a chance to pull the trigger...in others you may have time to prepare and aim well before things go south...I think its all about what you are confident shooting and hitting your mark with in a rushed and high adrenaline situation, within reason of course. I wouldnt consider anything less than 9mm as effective bear defense. Though I'm sure someone's great grandma killed a 10ft bear that was eating her chickens with a .22LR head shot somewhere along the line.
Hopefully they get the damn things delisted and back on the tag rosters. Maybe getting shot at and hunted on the regular will readjust their attitudes towards humans...or at least thin them out a bit.
As for carry options OP... I have FHF bino harness and I really like the Razco under binos kydex holsters. I've got one for G20 and P365. Very functional, light and super fast to draw from. I gotta say, carrying the p365 with 17rd mag is more pleasant than the g20 with 15rd weight and size wise.
Whatever route you go...Practice with what your gonna be shooting. I found my poi a bit different with hot/heavy 9mm vs practice and standard defensive rds.
Also found the P365 does NOT like hot hardcast stuff from Underwood despite being rated for +P and having no issues with other +p defensive rds.
Make sure your gun eats what you want to feed it well and reliably, I'd say that's more important than 9mm vs 10mm.