Highsider Mirror Adapter M10 x 1.25 Left Hand Thread to M8 x 1.25 - 304-043 - Dennis Kirk
Amazon.com: Evermotor Motorcycle Mirror Mount Thread Adapter M10 to M8 Bolts Screw Right Hand Thread 10mm RH to 8mm RH/LH Handlebars Mirror Fitting Reverse Thread Bolts for Motorcycles(3PCS) : Automotive