Hi Cees,
I looked at the one on SLS and it SEEMS to me that one is paying quite a lot more for a CTEK charger with the MB logo on it. However, if you are saying that it comes with the male to female plug that goes into the firewall do-dad than presumably that makes the difference. However, thinking laterally, do you know of a place where it is possible to get the male plug for the hole? If you don't, I will then try good old SLS.
Thanks,
James