I think it is. And I have not seen any available.
You might check the LMC, Scott Drake and Dennis Carpenter sites to see if they have something up and coming.
American Autowire does make factory harness reproductions, but this is likely pretty low volume and under the radar. But it could be worth a quick phone call anyway.
The alternator section is pretty straightforward though, so you could make your own as well. Unless you're wanting to keep it all original looking?
Good luck.
Paul