There is already an existing thread about this.
How about a pointer?
I'm surprised that you didn't find a perfect car charger on the web. I've a Surface Pro too. I'm using this: AVANTEK R31 3-Socket Cigarette Lighter Power Adapter DC Outlet Splitter Dual-Port USB Car Charger for couple of month.
I'll recommend you to use it. It has many other features too.