Flapping mirrors

Hello there, I own a VF1000 interceptor from 88, when driving more than 70, the mirrors flap.
I saw a topic about that but it’s old and doesn’t answer my question.
I would like to buy new ones, but the thread seems to be M10, but finethread.
So, normal M10 thread does not fit.
Does anyone recognize this?
Or does anyone know where I can get fitting mirrors?
Kind regards, Bart