I suppose that would probably be good information to include in each post — how to substitute the bean if you can’t come by the heirloom. This one, despite being called a black bean, most closely resembles a red kidney when cooked, so you could get away with a generic red bean. Luckily, with few exceptions, the beans don’t generally have a strikingly unique flavor, so it’s more the texture that you’re trying to match. Then again, there are beans that really do have chocolate overtones or peppery finishes, almost like wine. But with this, use a kidney bean.