Just found one, no problem It's M12, 17mm headed with a 1.25 thread pitch. It's also 10mm thick.
I couldn't find another straight away so I looked in a drawer in my Snap-On box where I store odd nuts and bolts and found another the same but not exactly the same, still 17mm headed but this one is much thicker, about 15mm thick. Might have come off a CBX550 I stripped back in the early 80s, it looks the same except for the width.. Which I suppose you could either cut to match or grind to match if it bothers you
You want one or both?
