The stock Miata washer nozzles just spray two streams of washer fluid near the windshield. My favorite kind of mod are the ones that borrow parts from another car, and Mazda happened to make a perfect replacement Miata washer nozzle when they designed the Mazda Tribune/Ford Escape.
Mazda Tribute: EC01-67-50YA
Ford Escape: YL8Z-17603-AA
Here is the main miata.net post about this mod.
Pop out the old nozzles from below to avoid breaking their plastic tabs. The new nozzles fit right into place, and the washer fluid tube should be long enough to reach them without issue.
The new nozzles spray a little high on the windshield when the car is parked, but they aim perfectly when the car is moving. Keep in mind that the angle of the hood is not the same for NA and NB Miatas.