We use LEDs from Diode Dynamics because they're the best ones we've found. They're made in the US to high standards, not just the minimum price. They've got constant-current circuitry to protect the bulbs from transients and offer a three year warranty.
The 194 is used for the trunk light on an NA (if equipped!) as well as the license plate/trunk lights on an NB - as well as thousands of other applications around the industry. You have the choice of cool white or warm white coloring - cool white looks like an LED, warm white looks more like an incandescent. 92 lumens for good visibility without making your plate the brightest part of your Miata!
A word of warning - be very careful when removing the housings for the NB license plate lights. They are easy to break, especially when it's cold outside.
Sold individually. One needed for the NA trunk, two needed for the NB license plate/trunk lights.