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Kitehard said...Speak to an engineering workshop, they should be able to do it for you for stuff all. It only takes about 5 minutes to insert a new helicoil.
Good winds,

Once again Kite hard hits the nail on the head. I've done a fair bit of work with helicoils (stripped alloy heads), it's only 5 min job, drill and tap, then screw in helicoil. They should be able to match the same thread as as your existing bolt, if not you may have to go to marine shop and get one, no big task.
Good luck