I have had the same problem, no stores in my city carry L2 cards it seems unless I want a dozen copies of the game dvd that now comes with it. So I ask for City of villians or City of Heroes and the stores have those game cards np. Look for the NC Soft label and it should work.
any NCsoft timecards will work with L2, I use Cov and Coh timecards on my L2 account since none of the stores carry L2 timecards and I have no CC, and there is a freind of mine that uses CoV, CoH, AA timecards to keep his account active