There was a Blitz, I believe they are Borg-Warner now, turbo kit for the 7M. It would be nice to have a KKK series turbo. HKS, Garrett and others used to make them as well. Unfortunately these were Japanese market kits. There was no US market at the time. You can call them to see if they just happen to have something collecting dust in the where house.
I would check with importers that bring in old JDM stuff. The Aussies are also a great source for this stuff. Aus market is the same as JDM. They love their cars down there. You can find all kinds of stuff. A big bonus is that importing from Australia is easy. There aren't as many import duties as with Japan. You can also find a used kit on ebay. They pop up there from time to time. I have even seen IHI turbos pop up occasionally. The stuff is out there, I just don't think you are going to find anything that is still new.