I had been missing of an helmet lock which I could operate with the same key as rest of the locks.
After doing some searching for an helmet lock for my GSA, I found an piece of information that helped a lot!
In BMW R1150GS they have a helmet lock and it is with the same key hole as new R1200GSA. So in I went and ordered an helmet lock with the BMW part number 51252313472 which is just the body of the helmet lock without the lock cylinder.
So I needed also that which apparently was part number 51257698204!
With these two I finally got the product together, after making my key to be the only one to open this lock which took about one hour to figure how this lock works!
This is how the lock looks like:
Now I just need to find a place where to put this in the bike.