There are several Norwegian online stores that sell cups. I know of one that is actually a cup store, the others are generally cloth diapering and/or babywearing stores that also sell a cup and some cloth pads (which is a great idea, since those who use cloth diapers should be more open to reusable alternatives :)). Two of these cloth diapers/babywearing have together opened a physical store in Trondheim, and it sells (drum roll, please) the Mooncup UK. It opened Nov 1st, is called Kenguruloftet & Krusedull, and is located at Nedre Bakklandet 22, 7014 Trondheim. I don't know of any other offline (so to speak) stores in Norway that sell cups, there really ought to be at least one in Oslo, but still. I'm happy! They also sell cloth pads, btw.
Norway being Norway (and thus, expensive), it's generally cheaper to order online from abroad, but this way, if you're in Trondheim, you don't have to wait for shipping, customs etc, and you can also avoid using your credit card online, if you don't want to. The last goes for their online stores as well, which accept both prepayments and cash on delivery.