You can generally find this at grocery stores, although I’m not sure I remember seeing it at my local Target (which has the new grocery section). It’s a little counter-intuitive to use, because of two things:
1) you put the whole yellow paper-covered package into the disposal, there’s no need to open the packet
2) you put the product in the disposal while running only a slight trickle of water into the sink, not a full-force stream of water
Frugalista Tip: You can also clean a garbage disposal with a combination of a tray of ice cubes and some cut-up lemon or limes.
There are a lot of expensive stainless steel sink cleaners out there. This is dead cheap; I found it online at Sur Le Table for $2.95 for this 12 oz canister. Most of the more expensive stainless cleansers are liquid spray-on formulations. This is a gritty powder like Ajax. Works miracles!
Disclaimer: I use both of these products and recommend them both. But this is a recommendation, not a guarantee. Read the labels, use common sense, etc.