Our local feed store has a product called Horse Fresh. It's made by Standlee. They told me it's the same thing as PDZ. I got a 25 lb bag of it for 6.99. It's kind of fine granular, slightly gray. I sprinkled it around in the shavings under the roosts.
https://standleeforage.com/products/horse-fresh
https://standleeforage.com/products/horse-fresh