Doug
Just answered your PM, in case anyone else has this problem too...
Try a little heat on the bolt and then use a metric allen that is just a wee bit larger than the 1/4' I believe that is in there now in a socket and try to force it in to the stripped head by tapping it in with a hammer to seat it as deep as you can and go from there. Word of caution, heat the bolt , not the tree. If it isn't the chrome tree, it could have a clear coating on it and would bubble or burn.
BTW...
If you re torquing a bolt, it's best to remove, clean and reinstall it and then re torque it applying locktight if called for. ALSO, do not confuse the allen bolts on the harley covers for the incorrect size. They are #27 torx and not the #25 that usually comes in the set of allens. They will fit and in some cases work, but you will strip the heads out.