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IIRC all seatbealt bolts are of a standard pitch you can find at Lowes or Home Depot.
My experience is that Lowes and H. Depot have squat for metric sized hardware. You need to have a bolt with a deep enough shoulder on it so the part that extends through the bar doesn't have threads on it. Ideally, the only part that should be threaded is the part that actually inserts into the threaded receptacle on the body. If you can find those at the hardware store, then yours has a better selection of metric hardware than mine does. I have a hell of a time finding metric hardware locally (without having to wait for mailorder). Just my experience.