You are wanting a single gun to perform two different duties. It is hard to find a single handgun that will serve well as a concealed carry weapon and also serve as a good bear defense weapon. So rather than just tell you what gun my buddy shoots I am going to give you something to think about.

The concealed carry weapon is going to be relatively small and chambered in a round suitable for killing humans not bears. A 45acp, 40s&w are by no means good bear defense rounds. A .357 magnum would be a minimum choice to defend off bear attacks. Preferably a 44 mag, 480 Ruger, 454 Cassul, etc... These are very powerful rounds capable of delivering a large payload of lead that will be able to break down large and thick bones and still get into the chest cavity of a bear. Rounds that are made for auto handguns generally are not loaded with bullets suitable to fending off a bear attack.

On the flip side a gun that is a good bear defense gun is going to relatively heavy and somewhat large thus not being very concealable and uncomfortable to wear under your clothes. The chamberings will also be waaaay more power than needed or wanted to effectively stop a human attacker. In this type of situation you want a low recoiling gun firing relatively light weight bullets that expand rapidly and transmit maximum shock in only about 6 - 7 inches but not ever penetrate the body.

If you must use a single gun for both concealed carry and bear defense then the only choice IMO is a double action revolver chambered in .357 magnum with a barrel length of 3-4 inches. Bullet choice for carry would be Federal 130 grain hydra shock, Remington 125 grain golden saber, Corbon power ball ammo, Winchester 145 grain silver tip HP, or others like these. For bear defense I would use Federals 180 grain cast core, Corbons 200 grain hard cast, Buffalo Bore 180 grain hard cast, or othres like these.