Well, it was harder to find a car than I initially expected. There are no cars dealers in the area, only a few private adds in the newspapers, and the only cars available are backpacker cars which I do not really trust.
So I decided to go for something else and hire a campervan instead:
It turned out to be quit affordable; it costs about $ 39,- a day + $ 26,- a day for zero Excess (eigen risico) so that about $ 2000,- for a 29 day trip up North. Not too bad really