They are a little pricey, but are very well made. I have a 1977 300D and got one that fit's in the center console, under the armrest. They even made a "custom" one for me that has the Zebrano wood finish.
Rickjordan is exactly right........drink holders are a necessity, especially with a 1 hour each way commute on Route 80 in NJ......gotta have the coffee.
Actually what would come in handy is an automotive "porta potty" for when you are stalled in traffic for a couple of hours. I hate to re-use the cup I just emptied.