Any dealer should be able to get you one. If they don't have one on the lot they should be able to track one down in the color combination you want within a matter of days. As many have mentioned in this forum, the Starmark warranty is good to get with these cars, if the original warranty is up. I have heard stories where people had dealers track down old models (like from the 60s) and it was no problem. There are a lot of these cars, I don't think it will be a problem.
1995 E420 - retired
1986 420SEL - retired