Looking for the 10mm nut that goes on the governor shaft. It's a 10mm super fine
"reverse" thread nut. It's for an MK1 TD Bosch VE pump.
I have gone to about 3 different bolts & supply shops with no luck. Supposedly the reverse/left handed thread nuts are very hard to find.
any info would be greatly appreciated.

Yea the round one is the old MK1 style then they got chaged to the hex.
I would do a web search and see if you can find any online suppliers.