Of course it's possible to order extra balls.
I expect the first Garnstudio delivery (a BIG delivery) next week (week 31), a little later than usual with the Fabel sock yarns, as they are also having holidays in Norway (so I’m already very happy I could get delivered now J). I will sort everything out and will also add single balls to my website, so anyone with a bigger size than mentioned on the pattern (or who wants to make it longer for instance) can buy extra balls. The nature white color (01) will follow in week 32 or 33, as that one is sold out at the factory at the moment.
Think this is the best way to do it? If you have any more questions, just ask me, I will be happy to help!
This will be so much fun, I will participate myself as well of course!