These cussed things have a habit of popping up and disappearing in supermarkets like rabbits at a shooting gallery. They're there, then they're not there. They're in the bean section, they're in the gourmet section, they're in the Italian section. Or they're not. They're a white Italian kidney bean.
White beans have a more similar taste.
When you do find them, buy several cans. Also, check Cost Plus, which always has a good variety of imported food at reasonable prices. I've been to every supermarket and cannot purchase sweeter ones. I do not know the answer to this question. It's probably a question of seasonality.