KazusaMinato Navy Yard is a Japanese producer of resin ship kits with a focus on 1/500 scale Imperial Japanese Naval subjects. In terms of IJN subjects, the KazusaMinato Navy Yard catalog can fill in some of the gaps in your collection of 1/500 scale models as it compliments those available through Nichimo. 

Their website is in mostly in Japanese (they have a page on the Taiho in English). You can use the AltaVista Babel Fish utility to translate this site.