WANTED: XT660 mirror (or part thereof)

[MirageF1AZ]

I'm looking for a left mirror for my XT 660.  In fact, I only really need the part indicated in this incredible artwork:

The adjusting nut in the top there must have stripped because the previous owner sealed it up with some Pratley Steel by the looks of it.
So now I can't tighten it up and it just flops in the wind.
Can anybody help?

Thanks
Dirk

 

[Crossed-up]

 

[Crossed-up]

 

[MirageF1AZ]