A year or so ago, the woodworking supply stores here in the Phoenix area discontinued carrying the PartA/B wood bleach, previously available in a 2-quart box.
On the internet I found that Klean Strip makes and sells this product, only in gallon sizes, so for about $90.00 you'll get a gallon of Part A and one of Part B. The only problem is that is is shipped, and you'll pay some hefty charges for shipping 2 gallons of hazardous chemicals.
Looking at Klean Strip's MSDS's (Material safety data sheets), the two parts are Hydrogen Peroxide and Sodium Hydroxide, respectively. I found an industrial janitorial supply company locally in Phoenix that sells these chemicals as cleaners/degreasers for about $5 a gallon, and in the concentrations similar to Klean Strip. For me, they worked as well as the expensive stuff.
Needless to say, I'm a little leary having the better part of two gallons of toxic chemicals in my shop, and I take care that they are stored properly. Having said all of this, if you use Part A and B wood bleach, please take all the necessary protective precautions--pretty potent stuff.