I'm pretty sure most prepaid cards have a lot of fees for overseas use.

I'd get him a CapOne account (or a card on your account) and just make it really clear that every dime he spends on the card is one he has to pay you back.

For the complete flyertalk guide to overseas credit/debit card use, see our wiki:

http://flyerguide.com/wiki/index.php...reign_Exchange

Unfortunately we don't list too many prepaid cards, though.