What I'm saying is that front head rests would work for the rears, or rears from other models without the flip down feature (the w201) would work. Take out one of your front head rests (carefully) and put it into the rear seat. My guess is that the posts are just a bit too long for it to go down all the way, but perhaps not. Anyway, I was just trying to make your search easier, lots more people with regular front seat head rests for sale than specific wagon head rests.

Good luck!

__________________
Daily Driver: 02 E430 4MATIC
In the family: '03 E500 // '04 ML500 // 64 220SE