I made a set for my old ZJ after getting hassled a few times... Truth be told, it needed them, with more than 90% of the tire exposed.
I used a set of truck stop mud flaps, trimmed down a bit, and bolted to some old running board ends and a little piece of angle iron. They were held on by two half inch head bolts and nuts per side, came off completely and cleanly in about one minute, and covered a lot more than they had to, which resulted in me being able to get away with the tires poking out of the body by a couple of inches.
This is what they looked like:
Weren't too pretty, but they worked.