For those who are wanting these cards in the UK, there will be a 6 card "Promo Pack" available in every copy of the April Edition of Official Nintendo Magazine in the UK!
I got my copy today with my 6 cards, but I'm not sure if the packs are random or set. I assume they're going to be the same as the ones on the Club Nintendo catalogue. Gonna see if I can pick some more up when the magazine hits stores later this week!