Up here in Fairbanks, AK the black vinyl type stuff with button snaps on it so it can be snapped on and off over the front grill of the truck seem to be pretty popular. The other thing that I've found convenient cheap and easy is take a piece of cardboard and cut it to block off some of the radiator... then slide it down in front of the radiator but behind the X strapping connecting the corners of the radiator. I've always cut the cardboard to the same width as the radiator and then sliced a boxed U shape out of the middle in order to provide sufficient cooling so it my truck doesn't overheat while idling.