I did a search on potassium bicarbonate (and incidently, I was well aware that sodium bicarbonate was baking soda--I guess I didn't clarify that baking soda = sodium bicarbonate).
Anyway, from what I learned at Google U this morning, potassium bicarbonate does produce the same results when you substitute it for bp when you bake. And, there are places online where you can order it. I'm going to look when I go to Chicago and also at some bulk stores here before I go. I'd never thought about subbing it out, but would like to sub it out for my folks. One of the few things my father does make is "tomato soup" and he adds bp to it.
I didn't realize that bp had the rda re: sodium in one teaspoon. My banana bread recipe uses twice that amount...