You may also be able to get it from a local feed supply company or a water well driller. I've purchased it for as little as $5.00 per bag from a feed supply company which I believe were 50 lb. bags. I thinks it's called sodium bentonite and some pig farmers add it to feed to increase the bulk of the feed.

If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.