How bout those defroster fans with a metal safety cage we used to screw to the truck dash for keeping the inside glass clear of fog in winter, then turn it around to cool you in summer.
One of those could mount on the hood, facing you or on a fender, or better yet, somewhere handy up on the
ROPS. A switch and fuse wired into your system should work, I would think.
Must admit I like Howierd3866's great idea of the car electric radiator fan, mounted up overhead. A soft, (safe) rubber blade might help?....(unless you need just a little off the top please).
Good Luck with it guys !
. . tug
PS: ...ah yes, just went back to the top and checked the links of Heath and Reddog. Yup, .. exactly what I was talking about. Swivel fans, plug into the lighter etc. Should have checked it prior to posting and wasting your time. Sorry.