There are optional front license plate holders, none are very pretty since the Miata really has no place to put on.
I'm one who'd really like to have a front plate, Arizona doesn't require one but when I park I get nasty looks because of no front plate and one very dedicated (to issuing tickets!) police officer took a stroll completly around the car so she could see the handicap plate on the back. Once she saw the plate she carefully checked the rest of the car, I wondered if she wanted to ticket me for something because I'd made her hike around the car?
Arizona no longer issues a sticker for the windshild and hanging the placard would work but only for the minute it would take someone to steal it from a convertible....