Try these:

www.waldusa.com/grosser.html
www.performances.com (canadian AMG parts source)
www.lorinser.com
www.brabus.com
www.opera-design.de
www.eris-car.de/indexdef.html

Or you can try convincing Renntech to sell body kits separate from the engine conversions:

__________________
Rainmaker
93 500E, 43k mi, Pics of upgrade parts
Evo II Wheels on Dunlop FM901 235/45x17s
94 Facelift
RennTech CF Airbox
RennTech ASR Defeat
RennTech Chip
1st Gear Start
97 Range Rover 4.6 HSE Vitesse, Yellow, "Tonka" (sold)