Hi Ben - Thanks for your reply. No I don't live in Japan, but am planning a trip in late October-November. I want to develop film as I go, but am not permitted to carry chemicals from New Zealand (they're regarded as dangerous goods!).
The site you gave me a link to is in Japanese, so I can't read it. It doesn't seem to have an English version.
Can I visit Silver Salt? Alternatively (I don't really want to do this), are there places where I can buy other developers?