I've used www.gamersloot.com a few times, when my game-time ran out on a late saturday night. They accept paypal and usually deliver within the hour. They send you an email with a link to a digital picture of your game-card. Works a treat.
Is there not an electronic way of topping up gametime? i.e. debit card online, instant gametime added to your account? I'm sure LotRO used something like that ... That'd be dodgy if you had to buy a physical 'card' every couple'a weeks to top up.