The NationStates Store page has just been updated! The main change is the removal of Google Wallet as a payment method, since Google is shutting that down, and the addition of Stripe.
PayPal is still supported.
As well as US Dollars, the Store now accepts Euros, British pounds, Canadian dollars, Australian dollars, New Zealand dollars, Swedish krona, Japanese yen, Hong Kong dollars, and Brazilian real.
The Store page now also forces an HTTPS connection (i.e. secure/encrypted) to view it, whereas previously this only happened once you started to buy something.
Please let me know of any problems or questions!