Feedstores sell it and TSC should. It cuts down on ammonia, but doesnt kill bugs, just so you're aware. Here, I can get it for about $10 for 40 lbs at the county co-op.
our county co-op carries it as well. Good stuff! I prefer food grade DE -- but this is nice for wet areas. Here is a link to some info on the product. http://www.sweetpdz.com/index.html