We have had a lot of requests on our flag design. We call them our "ding-a-lings"
We definitely got a kick out of it when the game announcer started calling them by their names as well.
Overall they are pretty simple.
We bought ATV flags from this site:
http://aditudegear.com/flags
We also bought a spring mount like this:
http://www.amazon.com/Wheeler-Whip-S.../dp/B005HJL94A
The spring mount was far too rigid so we went to Lowes and bought another spring and custom turned a plug to press fit it in the spring that was better suited for us. It is the same exact concept as the one I referenced above.
We then mounted this spring base to an angle bracket on the side of our poly-carbonate shields. You can kind of see the mounting application on the picture that the OP provided.
They work great for us and we love the visibility that they provide. They also help us square up on the defenses better because we can see them over the tall defenses.
Hopefully this helps!