....I just tapped and helicoiled a repair on one stem. It used M8 in a coarse thread (1.25, I think ?)

It is a nice stem, so I was thrilled to find the right sized helicoil repair kit.

But what the other guys said, take one out and go to the small hardware section of Home Depot,
among other places, that has a drawer of stainless, metric bolts.