Tough question because what they'll survive versus what they'll last for years shooting are two drastically different things. Realistically no antique is going to be 100% powerful enough to stop a bear... the calibers that most people would really put their trust in are beyond antiques (454, 44 magnum etc).
Now, if you want one for a fun plinker that runs on common ammo and could in theory make a bear's day miserable in a worst case scenario, you've got quite a few options. There's a trade off between common cals and powerful cals, since a lot of the old guns with the heaviest hitting cartridges were weird .50+ calibers. In this case I'm referring to the oddball .50 cal pryse models, big single or double barrel rolling block pistols, howda's etc. These all employ slow but very large grain bullets, but it's a strict case of handloading and you'll have to walk a fine line between functional and collectable which drives the price through the roof.
If you want something solid in a "smaller" caliber, then you're more in the common realm. You sacrifice some power in that you're limited to .44 and .45, so can't make up for lack of bullet weight by increasing the fps without risking eventual harm to the revolver, but you end up with a simpler to feed pistol. In these cases, you've got the SAA's, which are expensive but solid and reliable and often in modern cals like 44spl or 38spl; Reichsrevolvers which shoot 44 russian (10,6x25R German Ordnance) and are uber reliable, 1873 MAS revolvers in 11mm chambering or rechambered to 45acp or 455 webley which are more complicated but still very reliable and usually in great shape. In all these cases you have to choose your ammo carefully and select for low pressure lead only bullets to make sure your gun isn't unduly stressed and worn out prematurely. Can you get away with running higher pressures? I don't know...maybe? Do you want to find out you can't and end up with a parts gun?
If you merely want to annoy the bear while it chews on you, you can get into the .30-.40 caliber world of revolvers that're still eligible as antiques. Many of them are in amazing shape and are undervalued for what they are. They're often the most "modern" due to trends in design turning towards smaller calibers at the end of the antique eligible era, and are a ton of fun. Realistically I wouldn't choose an antique to carry if I was actually legitimately worried about bears, and you can't hunt with them in most provinces, so it comes down to how much you want to shoot them and how happy you are reloading.
Most importantly regardless of what gun you choose, with antiques you really get what you pay for. If you get a deal, be prepared for more difficulties in reloading or fixing something wrong with it. At 117+ years old minimum these can be simple issues to unfixable ones. Or you might just get a great deal and make us all jealous. If you do, post pics
P.S. There are some oddball guns out there, speaking specifically to the italian, belgian, austro-hungarian and spanish guns, that vary hugely in quality, but generally aren't considered super collectible. If you really do your research you might find a solid condition one that would fit the bill perfectly, but frankly, you'll probably have more luck with those listed above.
), antiques are tons of fun, and being able to legally shoot in the woods is one of the most freeing and relaxing things to do. There's really no downside to them, so may as well bite the bullet and buy one 
Everyone knows Thursdays are bear defence thread days!?
