The location nearest to Oslo Airport where I'm sure you can get this is the 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 that will fit a wide variety of appliances.
G-Sport Jessheim Ph: +47 63 97 27 37
Sport 1 Superstore Jessheim Ph: +47 63 97 20 63
Jernia Jessheim Storsenter Ph: +47 400 05 963