...there appears to be a few 500e500's listed here in the classifieds

I believe TomE500 has a ~35k 1994 example available for ~$50k- PM him for details.

there are also quite a few listed in autotrader.com starting in the lowerst price range

are you just testing the water (since you've indicated your next car will be in 2 yrs and an W140 S500) or you looking for someone else?

hope this helps
-fad