Looking around on the internet these kinds of traps seem to be primarily personal traps that are actually worn by the person who is active outdoors where the flies are present and hungry. I know from my own personal experience that deer and horse flies are not particularly respectful of standard repellents. They just zip on in, bite and feed, and pay no attention to the repellent that might keep mosquitoes away. At least one of the advertised traps is simply glue traps that you wear on the back of your hat, in the hope that the flies will at some point in their attack hit that colored patch first. Of course, the advertising really over-sells these kinds of things by essentially guaranteeing that all of the flies will go to the patch before they choose your neck or arm. 

Another kind is also a sticky trap but is essentially a large blue pot that presumably attracts the flies due to motion as the pot moves around on the back of a mower, for example, or on top of your head if you don't mind looking geeky, and the blue color that is touted to be attractive to these flies. From the new Pest West fly traps that are blue there is some evidence that blue is the color of choice for drawing flies. 

I would simply suggest that you yourself browse around the internet using "deer fly traps" as a search word. You will be fascinated by the choices that come up.