12V Motorbike mount (WVA9)

This is a simple mount I created for my Suzuki Bandit 1200S from year 2003. I was looking for a way to charge the batteries of my navigation system.

So I bought a socket for usual car charging cables. So far so good. But where to mount this thing?
The provided mounting piece was designed to mount it on the handle bar. I do not like it when there are too much thing mounted to the handlebar. So it needed to be put somewhere else. So one option left was screwing it to the plastik cover in the c