If your regular grocery stores do not stock regular corn meal mix, or just ground corn meal... A stop by any health/whole foods type store should do the trick.
If one can only find regular corn meal, and needs to add the leavening and flour, then that Pioneer recipe sounds really great!!! ( only I would use vegetable oil and not hydrogenated shortening... but shortening is probably fine!)
PS: sorry, my opinion... Even if one was from TN (my mom was too!) if you cain't make up a cornbread better'n Jiffy.... You just don't know how to bake up a cornbread!!! Hahahahaha!!!!!