I just bought the CoverMaster half cover in large. I think medium would work best for a naked. $30 bucks from a local shop and it comes with a storage bag too. It packs down into a real small package. I got the half cover so I don't have to let the bike completely cool off before covering it up.
+1 on the Dowco. It can be put on the bike when it is hot, has renforced lower section for hot pipes and a soft section for your headlight/windscreen. The cover also has a lifetime warrenty so if it ever rips all you do is mail it back for a new one.