The closest thing you'll find at these type of stores is 6%. I think I've seen "Clorox Outdoors" at Lowes before. I'm not sure but I believe it's only 6%. If you're looking for 12.5% you'll have to find a chemical supply. Some swimming pool supply companies have it on hand. A long time ago I used to buy it from Culligan. But it was expensive. Buying in large volume is by far cheaper if you're planning on using it all in the near future. I now purchase 53 gal. drums from Univar. They are nationwide so you may want to do a search for them near you. If you're gonna buy 6% from a box store go to Wal-Mart.
Jeff