i don't know of one right off hand of one what doesn't use the grill as a shell, i'd say you'll have to modify one, look for a 79-86 chevy phantom, it would be plenty large enough to modify to fit in the mazda front grille area....you'd probably have enough to make an insert for the opening in the front fiasca under the bumper!
NYTRDR, i hate you....i was reading down through here and i was planning to suggest the chevy grille, but you beat me to it.....
p.s. i dont really hate you