Need help with a plan B after flight delayed.

My family and I are flying into Oslo today on holiday and we had booked a car to drive to the place we booked in Kjelsås. It was originally gonna be tight with our flight getting in at 10:45 and Hertz closing at 11:30. Now our plane is delayed and we land at 11:30. We're trying to get a hold of Hertz to see if they can stay open for us but so far no luck.

I think our option is to take a taxi which I've heard is extremely expensive.

Or take the public transportation but I've heard the weather is bad right now.

Is there a third option?

Any help would be appreciated