I have been looking for alternatives as well. The limited selection of tires hurts, for $300 more than a set of OEM tires I can get a complete set of 20" rims, tires, and pressure sensors.
I have a few months before I replace them but I think I'm going with 275/45R20 tires on 20" American Racing Mainlines. They have a similar look to the OEMs.
http://www.americanracing.com/wheels/AR893/AR8933