I have an early model of a Japanese "Kate" level/torpedo bomber ( a Mania kit, I think, before the Hasegawa brand name was adopted?) I'd like to build the kit as the option belonging to Commander Fuchida, for whom I've always had a sneaking admiration- despite his leading an attack on my country (at Darwin)!! However at Pearl Harbor and Darwin, Fuchida carried 1,000 pounders . and the kit only offers a Long Lance Torpedo.
Is there an aftermarket company that makes WW2 Japanese ordnance as my scratch building skills are zilch?

Short answer - no (at least nothing I've come across). Hasegawa did the Kate with the 1,000 lb bomb (as well as in Fuchida's markings), but I've never seen any aftermarket Japanese ordnance.

Your best bet might be try trading the Long Lance to someone who wants to buld the torpedo version in return for their 1,000 lb bomb and the shackles.

Shane,

I'll look around in my spares box for one. If you don't hear back from me in a week, PM me and jog my memory.

A comment: Kates at Pearl were armed with 800 kg (1760 lb) armor piercing bombs converted from battleship shells. IIRC only a handful were made and they didn't work well. I have no idea if any were used at Darwin.

This is an impressive article on the bombs used at Pearl Harbor: http://www.j-aircraft.com/research/bill_sanborn/phmod21.pdf

Here's a photo from Oct 1945 of 500KG bombs at Rabual:
http://www.fold3.com/image/#46947370

Also, here's a place to post for parts -- whether seeking or offering:

"Official" Parts Yard

Thank you Frederick for posting links, just in time for me to paint my Val kit review bombs!