I just bought a Weathershield HP cover from Griot's Garage. As stated above, they have you fill out a form with 25+ measurements so that it will fit correctly. Mine fits perfect.
http://www.griotsgarage.com/p2p/sear...rrivals&page=1
Griot's charges a premium price, but their stuff is high quality, and if you have a problem, they fix it for you.