Now I see you are in Johnson County, so I'm sure you don't want to drive all the way through DFW to get seed potatoes. Also, now that I think about I only remember seeing seed potatoes in the spring.
I ran across a someplace (in Texas I thought) that specialized in many varieties of potatoes, but I can't find it now. (sorry)
I don't know about any of the stores near you, so if you have visited any of the local stores, please create a new post for each store in the "where" board.