It;s super easy to make you own, but if you don't want to mess with that, I seem to remember (during my visit last summer) Wal-Mart having it in their deli area where they keep the packaged fresh pastas and sauces. It's a small ball wrapped in plastic.
Around here, larger grocery stores carry premade dough in the same place you can get premade uncooked pizzas. Also, you might want to check Schwanns frozen dealer. I know there is an equivelent here and they sell frozen premade dough. I still like to make my own.