I've never hunted in areas with grizzlies but I carried a 1911 with cast flat points when we were in Yellowstone.
At handgun speeds most bullets won't deform much, if at all, if cast from a somewhat softer alloy. At rifle speeds maybe 'hard cast' is a need for deep penetration, but at handgun speeds, 'hard cast' is more of a marketing term than anything you actually *need*.
And if I had a pistol that wouldn't feed wide-meplat flat points, but I wanted deep penetration, I'd very likely just buy some flat-point FMJ type practice ammo. At the end of the day the selling point of 'hard cast' ammo is deep penetration and tissue damage caused along the way by the wide meplat. Well, a basic flat point FMJ or truncated cone bullet like a lot of cheaper 10mm ammo has, will do the exact same thing, albeit it usually with a slightly smaller meplat, and for a lot cheaper. And if the meplat being smaller means smaller wound channels, it also means a deeper wound channel.
Don't overthink it. Your best bet with a charging grizzly is to make a CNS shot and your best likelihood of doing that unless you're an insanely good pistol shot is to be able to shoot multiple shots.
When I lived in east TN I very unintentionally walked up on a black bear one day. I was squirrel hunting, it heard me and let me walk up on it before it spooked and took off the opposite direction. Its speed scared me. Had it wanted to hurt me I would have died with my .22 slung over my shoulder. Bears are fast when they want to be.
CCI makes a Blazer load in 10mm with a 200 grain flat point FMJ. That's exactly what I'd buy if I needed a box of 10mm 'bear load' tomorrow. Not because it's cheaper, but because the smaller meplat bullet is more likely to feed well in a gun that's already shown to be finicky.
