I modelled one using the US helmet as a basis. See this thread:
Scroll down to April 1st’s post. The link should take you close to the beginning of that project. He turned out pretty well.
A little farther down you can see the start of my Ukrainian tractor build as well. That one really did turn out nice, but I’m withholding the “unveiling” (as the jackasses from American Chopper used to say) until the right venue.