I am not familiar with Dusseldorf very much and I wonder if anyone could guide me by recommending any place close to the central HBF or Ko Galleria that would happen to sell a headphone adaptor for planes?

I cannot find my original one and I don't really want to possibly buy a hugely overpriced one in the airport if it's easy to buy one somewhere for what they are actually worth.

I'm going in to the city anyway, so I thought it may be worth asking.

In here everyone should know what i'm talking about but just incase, here's a pic.