What about this stuff? If found it when I was looking for sand...
"Hog Fuel
Hog Fuel is the rancher's choice for controlling mud in arenas, padocks, and barns. A good layer of Hog Fuel provides a cushioned barrier to keep your animals dry and comfortable during the wet time of the year.
Hog Fuel is an unprocessed mix of barks and wood fiber. The size of the material varies, but is large enough to take a long time to break down.
Recommended Uses
Hog fuel is terrific for mud control and around construction sites. It drains well and can be used for animal beddings or horse arenas.
Application
Apply at a rate of 3" to 12" for mud control, depending upon conditions. "
Also, beach sand or river sand...any difference other than price?
Hog fuel is $16, river sand $20 and Beach sand $28