We only accept the payment methods listed on the purchase site. The alternative is to ask a friend with paypal or something to purchase the key for you, and then you pay them through said payment method.
You can try sending an email to [email protected] as they are the staff that handle payments and keys, no one on the forums directly here deals with that. I was simply stating the information I have at hand, and giving you an option off the top of my head, you COULD try asking the support on their email though.