I've got to get something, too. We use a tractor in our backyard, and the flies are bad. We clean up the poop daily and don't leave stuff sitting around, but it doesn't seem to matter. The girls don't care about going after the flies, either. They loved gnats when they were chicks, and they ate a snail yesterday like there was no tomorrow...but no flies.
Last year we tried one of those bag fly traps with "putrescent egg white and yeast" as the attractant. I kept smelling decomposition, and sure enough, it was the trap. Eww! I'm going to have to look for that disposable trap that you posted.