Killjoy,
I'll put this out there, BUT with a caveat that i could be way off mark - if so, i hope somebody with better knowledge will step in...
Gunze Sangyo make a colour called Interior Green. I'm fairly certain that it's a close match to Green Zinc Chromate. I can't remember the no. code, I think it's H50something...
I've seen instructions which call for Green Zinc Chromate, then give the equivalent Gunze Sangyo colour as Interior Green.
However, I can't be 100% and hopefully somebody out there will help, but i thought i'd just let you know. I know Gunze are hard to get in the US now, but if you find some, might be worth checking out.
Unfortunately, i'm not familiar enough with Tamiya to assist on that front.
cml