I would also recommend fish (there's more than tuna for variety) The cheapest will be frozen and tinned stuff. In tinned, look for 'Stabbur'. The mackrel in tomato sauce isn't too bad (it needs bread or something to go with it). Fresh bread is good, and easy to come by in Norway, so you can buy bread and various things to go on it, and make your own sandwiches.
Frozen meats, I think you could buy, and let it thaw as you ride, as long as it is in a well sealed bag. Then, it will be ready for cooking at the end of a day.
The best quality fish will come from the boats, and sometimes you can get a bargain, as well. If you are near a harbour towards the end of a day, ask the locals if there is a place nearby to meet the fishing boats.
Another possibility is packet soups. They tend to be of somewhat better quality and variety in Norway, as tinned soups are less common. I prefer them mixed in with some pasta or rice, and maybe a tin of beans, depending on the soup.
“In some ways, it is easier to be a dissident, for then one is without responsibility.”
― Nelson Mandela, Long Walk to Freedom