Jeremy -
I used to have a freshwater planted tank myself and had a hard time finding plants here in S.A. Before they closed, I would get plants from Aquarium Sales and Service. Also, a couple of the PetsMarts would have a decent selection, but that would depend on the department manager and if you got there within a day or two of when the orders came in. The only other place in S.A. that sometimes has a variety of plants is Fintique on West Avenue. I would always check out Aquatek when I was in Austin as they were usually better than anything here.