@grammyskiles- I found a few places online that you can purchase sour mash for homemade bread. Check out the Taste of Kentucky website.
Also, I believe that Persian Markets often carry the sour mash you are looking for. There's a great one in Sterling, Virginia that definitely sells the product you're seeking. The name of the place is Persian Market and Bakery. Other foreign food stores/markets probably carry it as well.