I don’t see a recent thread on these, but I do see that various folks have used the Horse Pal trap over the years. (And that the Epps trap did not get good reviews.)
So, is anyone using the Horse Pal and are you (still) happy with it? http://www.bitingflies.com/
What about the Spalding H-Trap which appears to be the same concept? https://www.spalding-labs.com/products/fly_control_products/fly_traps/p/h_trap.aspx
(Which came first? The HP is supposed to be patented, how can there be something that similar?)