Michigan DNR requires the flag be 10' from the ground when mounted at a standstill. Must be safety orange, rectangular in shape and a solid material. For "sit in" automotive style seating, the flag must mount to the front most portion of the vehicle. For motorcycles/quads/3 wheelers it must mount on the rear of the vehicle.
I found this place that has a clamp on mount that mounts to the front tow hook. They also have a vertical style for HD trucks.
Laser cut with welded grade 8 hardware included. Hit the dunes in style with this easy to install dune flag mount. Powdercoated in Satin black for years of abuse. Fits ANY Tow hook up to 0.750" thick.
www.jdscustoms.com
These ones are way cheaper but look like something you could make with some scrap metal if you have the right size laying around.