If you handload the 45 is the obvious answer, it can be loaded pretty hot.You shouldn't have any trouble getting 1200 FPS or better with a 300 gr round out of a rifle, that's going to hit pretty hard.
I have a .357 and while I have no trouble taking it deer hunting I'd be reluctant to go after a bear with it, unless I had no choice.
Then again, which rifle do you shoot better? All the power in the world is useless if you miss, or don't have confidence in your ability to hit with it.
I was even thinking about getting a 454 Casull lever action. Then I could have the best of both worlds 45 Colt and 454.I would think the 45 would have a bit of an edge , heavier bullet.
But I can't say for sure as I have neither and am looking for both ( 24" octagon barrel of course )
I found two 1894 45 Colt cowboy action and both for sale. With the Octagon and long barrel seem pretty heavy but I would gather they could hold one heck of a charge due to the weight back on the recoil.1200fps? Here is A load for bears. 300 grain WFN/LBT /H110 32,500 CUP 1705 fps. I deleted the charge weight. as it was slightly higher than I have tried personally. A .357 does not even come close to this power level. Go with the .45.
Chiappa makes them The ones I have seen look good. Have not shot one. yetI have a big shoot to go to today but that looks like a good article so I'm bookmarking it to
Very few companies make 1892's, I know Rossi, Winchester and Cimarron do.