I've been planning our trip to Norway in September with lots of great suggestions from the forum. We're doing the DIY NIN tour because it is cheaper and just wanted to share that you CAN buy the minipris tickets from Oslo to Flam online from NSB.no with a US (or Canadian) credit card. I called NSB.no and they told me to select the paypal option when checking out, then you can pay with your credit card even if you don't have a paypal account. Super easy! Hope this helps future travelers.