I don't know of any in the south, per se, but you can try looking into Prairie Moon Nursery in Minnesota or Outsidepride in Oregon. Treeseeds also seems good for rare
trees that you can't get elsewhere, but they are a bit expensive.
Also, a place in Tennessee, whom I decided not to use because I don't need that many plants, sells seedlings in bulk at pretty low prices. The only catch is you usually have to buy at least 50-100 specimens at a time, so if they
sell each one for .80c, you're still going to be paying a pretty hefty price tag. But, at least you'd get your money's worth.
I just looked them up again real quick, it was Tennessee Wholesale Nursery.
Of
course, Texas is a very different region, so I hope you can find, at least, some of what you're looking for. Good luck.