I don't know where you can get spare of those types of stud.

I know what you're refering to though.

The end that has the appearance of a round file is a push fit into the handle, and the rough surface is what holds it captive in the handle.

The only two suggestions that I can think of is to either use a similar size normal stud

(M6, M8 or whatever size it is) and bond it into the hole using araldite or similar, or get a spare handle from a breakers or someone breaking their car on here.

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