I haven't been able to find anything about leftover canisters.
However, you could get a new one at the airport. Not at the actual airport, but at a gas station that is directly opposite the airport. I just called them and they sell a gas canister called the Coleman C500. That's the only one they have. But it might fit your stove. If it doesn't fit, then read on.
The location nearest to Oslo Airport where I'm sure you can get this is the neighbour town of Jessheim. I have found a number of businesses there that almost certainly sell it. I have also phoned the first one on the list, and they have confirmed that they have gas canisters for a variety of stoves.
G-Sport Jessheim +47 63 97 27 37
Sport 1 Superstore Jessheim +47 63 97 20 63
Jernia Jessheim Storsenter +47 400 05 963
These businesses are all within walking distance of each other, so if one doesn't have what you're looking for, you can easily walk to the next one. They all open at 10 and close around 8 or 9 on weekdays.
This town is about 10 km from the airport. Will you be renting a car? If so, it's perfectly reasonable to stop by Jessheim and buy everything there. If heading north, though, then it's wiser to stop by Eidsvoll and visit the equivalent shops there.
What is your first destination after the airport? The most convenient thing would be to just buy it there. E.G. if you're taking the express train to Oslo Central Station, then just get the canister at a sports store there. If you're going to Lillehammer, then buy it there, etc. Even small towns usually have a sports or hardware store. You might want to call them first (they will almost always speak decent English) to make sure they have what you need.
So, if you buy it in a town you'll already be passing through on your journey, you may save yourself a possible detour through Jessheim or Eidsvoll.
Although it might exist, I'm not personally aware of any place where you can get second hand canisters. The easiest way may be to buy a new one.