It's funny, but I was looking for a source of those things a while back. The only place I could find that carried them, sold them mostly to packers, shippers, manufacturers... people that need to buy them by the truckload. Consequently, it just wasn't cost effective for me to buy them for what I wanted them for (long-term storage of luggage).
Now I find out that I coulda used kitty litter?
Harumph...