a one shot kill on any bear with a hand gun is very rare. Not impossible but not likely.
While I realize that this is a forum about guns as opposed to cycling (or perhaps common sense), and will defer to others on the gun question, I have to suspect that you may be expecting too much from guns while maybe not estimating risks accurately.
Not only is it unlikely that you will ever kill a bear with any handgun (just as it is very unlikely that you encounter an aggressive bear that requires you to try to shoot it) I find your assumption that you might be able to stop a charging mountain lion with a handgun far fetched (just as it's unlikely that you encounter one of those). Those critters are fast, and getting a lethal shot off even if one is standing still with an apple on its head isn't easy. Yet you're going to do it while riding a recumbent?
Meanwhile, although fears vary, you might be more practically protected with a small handgun loaded with snake shot, especially if you plan to camp. Not sure, but I suspect that the risks of one of those slithering into your camp site are greater than a charging mountain lion or aggressive bear.
There is also weight to consider. How much weight do you want to add to your cargo in the form of guns and ammo that you almost certainly won't ever need or be able to use effectively if you do need it?
Having been in your situation before, I carried a little old .38 special with the first shot snake shot and the remainder regular self-defense loads, a well as pepper spray. It was hardly a perfect self-defense set up, but was light enough and covered the basic bases. Also, I could actually shoot the .38 special with reasonable accuracy, which is another main feature you look for in a weapon that suits your specific needs.
Of course, I never needed any of it, but then again felt better at least having something in case--and there are two-legged predators to worry about too.
My advice is therefore to stick with the gun you have, especially since you are comfortable with it, and just not plan on having to try to shoot a bear (and in the outside chance you do try, you can find out if it will take a bear out then). If you buy a second, a .22 loaded with snake shot is probably the best choice. Also, get a couple things of pepper spray to attach to your handlebars. Realistically, you're more likely to be chased by dogs, against which pepper spray usually works, than attacked by a wild animal (unless it's a snake).