I use a mineral-salt "rock" at home and take a year-old "rock" when I travel. The one I carry is about the size and shape of half a golf ball.
I find these rocks (some call them crystals) work for me. They irritate some people's skin and for other people they are not strong enough. By wetting the thing I can get enough salt on my skin to keep the odor-causing bacteria at bay.
EDIT: A new "rock" is a bit bigger than a golf ball. It's easier to hold, since it's used wet. For me a new one lasts just over a year for about $10 or $12.
"The belief that there is only one truth, and that oneself is in possession of it, is the root of all evil in the world."-- Max Born, Nobel Physicist