I don't have a hat. I made something similar to the ones on the sideview mirrors. I mounted it on a pole and have a little box for the pole to sit in. I have to take it out when I go under a tree. It is not unusual to end up with 70-100 deerflies stuck to the trap after a 2 hour mowing session.

"A fanatic is someone who can't change his mind and won't change the subject" Churchill