I think you are a bit optimistic on the performance of the 29.
Here is a web page testing various 10mm loads at various barrel length and a "real world" example.
(statement of intent)
www.ballisticsbytheinch.com
It suggests the difference between a 3.5" 29 and a 6" 20/21/40 could be between 100-150 fps.
I haven't pushed it this far yet but I am aiming for 1,350 fps with a Hornady 180 XTP. The XTP seems to expand well, penetrate deep, retain most of it's mass at velocity near that (in ballistic gelatin) and heavier bullets seem to lose too much muzzle velocity to maintain the same energy. Bear might be tougher than ballistic gelatin but I still think a 180 XTP is about the biggest punch you can get from a semi-auto. .460 Rowland is another that people look at but the .451 hollow points are designed to work closer to .45 ACP velocities so I think a cast bullet would need to be used and then you will get great penetration but lose expansion (mostly), temporary wound cavity and wound cavity width.
An interesting thing from that site, 357SIG keeps up with 10mm kinetic energy pretty well. I've got a 5.32" conversion barrel for my Glock 22. Could it be a backup bear gun? I wouldn't try it, I don't think the 125ish grain bullets that it uses would hold together very well, expansion would be less and if the bullet does come apart, penetration would certainly suffer.
An Automag, Desert Eagle or other huge semi-auto pistol might improve on a 10mm but I think the logical and cheaper step up is to a .44 Magnum revolver and then up the ladder with .480 Ruger, .454 Casull, .475 Linebaugh, .500 S&W and other big bore revolver cartridges.