If looking for just a better single cupholder, Pep Boys and most big auto parts stores carry converter inserts which let you morph a small cupholder (such as in the Xfire) to one that will hold any size mug. These products vary in quality and stability, check your application I'm not aware of any product that converts a single cupholder into a duo.

Not sure I agree that the Germans at Benz were perplexed by Chrysler's cupholder request; I thought the SLK itself originally had 2 upfront, that were criticized for sort of interfering with the driver's vision.