Coolant leak (part number)

My coolant seems to run low every week and a half/2weeks. Ive noticed small puddles after ive been sitting in the car.

Was told this was a common problem? Quoted from another site

If u have any coolant leaks its bound to be the o ring for the coolant housing on the side of the cylinder head leaking.
The o rings become brittle and perish causing a leak

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Doe's anyone have the part number for this "O ring"? Is it a pricey fix?

Also my back window scoosher isnt working either, Any common faults here?

Ive got a 2003 2.0 FSI

Thanks
Mick