Have you ever seen those army knife like thread/pitch gauge kits? You can find some that are quite extensive, and they might help you. Although, if Rick is correct, you may not be able to find it at all, if its some custom thing.
Looks like something between M8 X 1.0 and M8 by 1.25. Which is not much help. I also have the very small guides but will need my microscope to check for you. I will do so later. There's many more folks much smarter than me to figure this out (Rick H...I was think of you! .