Kühlschrank is the name for a fridge in German. I saw Kühlbox listed in the description as well as Kühlfach (cooling compartment).
A quick Googly search found two of them, but they were both D2 fridges and also much cheaper at around EUR400. I'm now quite tempted by the idea of a fridge in the back of my A8L D2.
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2010 B8 S5 Sportback quattro 3.0 Supercharged in Sprint Blue (current girlfriend)
2000 D2 A8L quattro 4.2 in Audi silver (my ex-girlfriend)