Pit Road is a Japanese outfit and the kits go in and out of production. THis makes supplies iffy at best. Are you looking for the 1/350 resin I-400 model or one of the polystyrene kits in 1/350?
Here's a link to Freetime Hobbies, but the kit is out of stock.http://www.freetimehobbies.com/PITWB10/
Freetime is the old Pacific Front site, a really good source for naval models.