I dunno man. I thought Limited came with Karkand. Either way I don't really play any of the karkand maps so whatever seems cheapest to you will do.
It's 27 bucks on this site.
Battlefield 3 PC - OzSave.com
It's a legit site too, I pre-ordered 2 copies of Diablo 3 off them, but they had some stock issues so it took a while but they sent cd-keys ahead of time. No reason why they can't do the same for you.