Well, prepaid debit cards are now under new restrictions. Ones that are allowed to be used outside the U.S. generally require that the card be registered online, so most issuers restrict use to inside the U.S. only.
Would you find out for sure if these truly can be used for purchases outside the U.S.?
There are a few prepaid cards that can be used internationally, but many don't allow it. In general, be wary of any card issued by a bank in the US. Due to recent legislation limiting interchange fees, many banks are routing transactions to different networks with lower fees, and many of these networks are not international. Even when international payments are processed, it may be limited to certain countries.
Many online stores verify the billing address (or at least ZIP code) so you need to register your address if you want to buy from them. This usually only works for US addresses.
BTW, try searching for "visa gift card" on bitmit for some examples.
