Booking domestic flights from outside Japan

[becciwhitton5094]

Hi, I'm visiting Japan in late September / early October, and would like to fly down to Okinawa as part of our trip. However, I'm having trouble finding a way to book the flights from outside Japan. I found cheap flights on the JAL website, but I couldn't buy them because it wouldn't accept my credit card. I've tried to find flights through ANA and Skymark, but it seems like they don't show flights more than 3 months in advance?? Does anyone have any tips on buying domestic flights from outside Japan? I tried asking my travel agent about the ANA air pass and other special deals I saw advertised on the internet, but they said they'd either never heard of them or couldn't book them, so I gave up on that route.

Thanks!