Its nowhere remotely near as inexpensive as a $4 rock that lasts 10 years, but I have found plain old alcohol based hand-sanitizer does the exact same thing.
A $4 pump bottle from walgreens lasts 2 people about 3 months.
I've used the rock before, but I find the sanitizer easier and more comfortable to use (no slippery, no sharp edges, easier to get the whole weird shaped underarm area, and easy to refill little travel containers from the bulk bottle, so as to put one in the car, one in the gym bag, etc.
Even if you don't use it at home, its a good trick to have when you are out in the world, getting unexpectedly sweaty, and come across a public hand sanitizer station.