I have one from Cascade for my Eclipse, and one from Stinger for another car.

The Cascade was custom built for me, and was around $700. The Stinger is a little more "main stream", and will se you back about $350 or so.

Depending on what part of town you live, I might suggest some of the stereo shops. Most all of them can order it for you. I know Area41 (IA Sponsor) or Traffic Jams can bothe get one for you.