Check your hardware stores (Lowe's, Home Depot), I found ours at Menard's but doesn't look like you have any of those there. I also found 10% at WalMart. Our pool store had the higher % too but it cost more there.
Pool Warehouse. We have one in Beaumont, thus I assume there is most likely one in Beaumont. Leslies also carries it, as well as Lowe's from time to time. Although i question how old some of the stuff is at Lowes.