I just ordered a windproof jacket from aero tech designs a few days back. It hasn't come yet, but I've had good experiences with their bike shorts, so I decided to give the jacket a shot.
http://aerotechdesigns.com/cycling-j...erproof_jacket
It only comes in red in 3X and 4X, unfortunately, but hey, I've learned to live with limitations at this size.
Also, if you order by 11/30, you can use the coupon code "Cornucopia" and get 15% off anything in the store.