I've had really good luck with this from Cal Car Cover:
http://www.calcarcover.com/product.aspx?id=629&cid=
It has 4 straps that have soft hooks that hook under the 4 fenders. I bot the one for a Miata 7+ years ago, however I think that they may have one now for a Cobra. It stores in a really small bag - perfect for the Cobra.