I saw some on eBay but it looks a little different from the one you found, the rear top vents seem to kick up much higher than the unit you have, presumably making it taller
GENUINE MERCEDES S CLASS REAR HEATER AIR CON UNIT A2208300262 E311/7 | eBay
As the years bring style changes so does the unit change in designs to accommodate the change in the design of the center console.
That year is out of a 2003 I believe, and yes the dimensions are different.
Yaughn has one out of a 2002 I think he said it was out of and he gave me the dimensions of it but I no longer have it.
I'm sure if you contact him he will be glade to give you the dimensions of it.
I think he said it was a little shorter but taller than the one I have
That unit has servo operated doors so it may be more desirable, but the controls are also different from the one I have.
I have been looking for a newer version of the unit such as that in the yards so I can see what the differences are and maybe go to the newer version. But until that happens I'm sticking with what I have.
I've seen versions of the unit going up to 2013. Not sure if Mercedes continued making them after that year.
Now that the word is out they may be harder to find