This seems like a really serious omission, and I'm not at all sure what to do about it. Ideally, I'd find a version of the font with an @ included and use it. Failing that, I might redesign the card, since the character's not used in the main graphics, and a contrasting font would work. There's even something to be said for using clearer text than the logo.
Still, I'm disappointed. I have no idea why they'd leave it out.