Not sure if this is the best folder for this post so feel free to move.
I am now the proud owner of the best fly spray dispenser ever!
It was $10 at Home Depot - empty, of course. It works in the same way as the sprayers for RoundUp work - pump and spray. No more PST PST PST noise to aggravate your horse!
I got the 1 gallon size but it comes in bigger sizes.