Discovery/Composition Media Quadlock Extender?

Looking to add an inline amplifier and subwoofer to a MY18 Tiguan without cutting/tapping/splicing the factory wiring.

Thought the best way would be to utilise a quadlock extender similar to this to incorporate the required wiring changes:

Ali Express 52 pin Quadlock Extender

Does anyone know of a local source for these 52pin versions, or are the brown plug male+female combination which fits into the quadlock available by themselves anywhere?

Thanks for any advice!