I deal with stripped bolt holes frequently in my occupation. My preferred repair is a Keensert. Not sure if it will work in your application or if they offer them in the size you need but I would venture to guess you won't spend $400+ dollars to repair one hole.

Here's a link that kind of explains them. You might do some more googling and see if you can find more info.

http://www.repairengineering.com/keensert.html