I have one for my SPF from California Car Cover. I got one that is made out of a T-shirt type material. It's just to keep the dust off it while in the garage. But, they make all weather covers too. They fit like a glove, and are great quality. I also have a black one for my black '03 Cobra.
Here is my SPF....
Here is a link. There are a bunch of types available. You can also select if it's a 289 Cobra, 427 Cobra.. and with or without roll bar.
California Car Cover Company - Find a Cover