Try the Nokia Concept Store downtown Oslo, I think it may be in the shopping centre called Byporten though Im not 100% on that.

Also: any Telenor store will be selling the N9, probably cheaper than the Concept store if you get a Prat 99 subscription (which at least when I bought it was the lowest total price for the phone).

The latter method with the Prat 99 subscription allows you to unlock the device free of charge for use with other operators, btw, but you will have to pay 99 crowns a month for 12 months. Still the total price should be the lowest youre able to get it for.