I saw where a spare donut for a 2003 to 2010 Miata has a solution. But what about a 2011?

Where did your spare go? Dealer parts dept. should be able to get you one- but the really trick way to go, for a sports car, is just buy a fifth wheel to match the 4 on the ground- same wheel and tire- and throw it in your trunk- if you ever hit a curb and bend a wheel- milagro! you whip out your spare and still have matching wheels! Plus with that cool-lookin' spare, you open your trunk at car shows and the girls are impressed with your wisdom and style