Dichlor => http://pool9.net/ssr/

For every 10 ppm of chlorine, dichlor adds 9 ppm of stabilizer. If you can get a 24 pack at Sams Club that would be idea. They are one of the few stores reliably selling un-diluted dichlor. Otherwise, you may have to get it from Amazon. You can check Lowes, Home Depot, and Ace -- dichlor that shows 56% or higher available chlorine (NOT: 56% dichlor!!) is the good stuff.

http://pool9.net/sams-dichlor24/