I just came back from mb dealer. They told me that the water pump is not longer available and the asking price was 770€.
This is NOT a part to buy at the dealer even if available. 770€ is totally insane. There are a number of suppliers of this pump in both long and short versions. Prices at the low end would be maybe 50€ and at the high end 150€. These are all well known manufacturers such as Febi, Laso, Graf and more. I chose the Laso pump back in 2011, I think it cost me about $100 or so, and came recommended by one of our known suppliers here, Dave Gallon.
You'll see that Peter h noted a Febi for under 50€.
It was Joe Alexander to wisely told me to throw out the gasket that came with the aftermarket water pump, and use the MB OEM unit. This set me back a whopping $4 or so. But it was very clear that the gasket was superior to the one that came with the pump.