Mirror mounting bolt and collar

[w123driver]

My coworker gave me a mirror from Aprilia to replace broken mirror on my Breva. Aprilia's mirror has mounting bolt thread broken off and I was hoping to use existing mounting bolt and locking collar from original Breva mirror on Aprilia, but turned out Aprlia's mirror has smaller diameter stem than MG, so I would need to find mounting bolt/collar. The bolt has 10 x 1.25 mm thread  and the stem is 10 mm  in diameter. If anyone knows where to order the bolt would be much appreciated.