HELP! Remote side nutty-ness

Any idea where I can source the nut that goes on the remote mirror joystick INSIDE the door. Not the chrome bezel/not facing the car's interior. Or at least what the thread count/pitch is?

Pic shows the hex headed View attachment 1715524437 buggar...

Resto/Repop houses don't show any such item....

Hardware store fine thread isn't fine enough it appears...

HELP...

Got a junk mirror that has said nut? Let's make a deal for the whole thing!

TIA
On this subject, my remote mirror won’t stay in place. Keep having to adjust it. How to tighten?