Tepary beans can be bought at Seeds of Change and Native Seeds

If you can find the kind of beans you want in a supermarket you might be able to grow them. I looked at some online seed vendors and they wanted $45 a pound for Black Soybean seeds. You can buy the same dried beans in a Korean market for $2 a pound as food and they will grow. I tested them and got 100% germination.

Here is one place for some unusual beans. There are plenty more.
SMAC

You might look through this link.
seed&supply vendors

DarJones