Replacement seat belt bolt

I’ve just had my seat belt reconditioned on my 2002 3 door but when putting it back in it seems the bolt that holds the seat belt rail on won’t go all the way in. I think I may have cross threaded it and want another to make sure, but can’t for the life of me find the part or part number. It’s the 17mm one that holds the rail into the side of the car
 
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