You would have to get a friend who lives near a 7-11 to get you the card and send it to you.
Just a minor point to save a postage stamp, but there is no card and no need to send it. Airtime top-ups are printed on the cash register receipt. You call 611 from the phone you want to top up, then key in the code on the receipt. That means your friend doesn't have to send you anything; just tell you the top-up code.