Yes, either a hardware store or bike shop will likely have a replacement metric bolt, but what you need depends on what you mean by "stripped." When you say it was not the wrong allen wrench is sounds as if the allen fitting on the bolt is rounded off. If that is the case, then a replacement bolt should do the trick. If the bolt turns OK but never tightens and the threads on the bolt are gone, then again a bolt will do it. If the bolt threads look good but it won't tighten you are likely into a new stem - not worth it to try a repair.