Salt/Mineral Blocks with natural fly repellents??

My in-laws found a mineral "salt" block for cattle that has a natural fly repellent in it. And they wanted to get it and give it to the horses. I know horses and cattle have different needs, and usually require different minerals. So I was wondering if any one on here has ever found a mineral or salt block similar to this for horses?
Just a question.
Thanks!!

Fleet Farm sells a mineral block for horses that has fly repellent.
33.3 Lb. Fly Control Block By Stockade - Mills Fleet Farm

Awesome!! Thank you!!! :)