If you take the bolt down to any half decent hardware store, generally plumbing shops are pretty decent, and they'll be able to find a tap and helicoil kit for the size of the bolt, along with the right size drill bit.
If you get a whole kit it should come with guidelines, if not its fairly simple, take your time drilling the mount out and make sure you get all of the debris out before trying to tap it. When it comes to tapping, do 2 full rotations in, then one back, this will help clear any swarf out as your going and make it alot easier, once you're done with that thread the helicoil in and job done.