Off topic: Suggestions on dulling rivets in leather?

So my halloween mask came in, dieselpunk ish leather mask, and it is great... Except they used super shiny steel (stainless?) rivets on black leather which looks more..... Bondagey than I was going for. Not kink shaming or anything, just incongruous with the rest of the costume.

So, question: what would the best way to take the shine out of these rivets be without damaging the leather?

My first thought was sanding, but I’d almost certainly damage the leather. Similarly I think paint would be inpersice.

The internet suggested blueing, which seems like a faff but might be worth looking in to. Suggestions for vinegar or lemon juice to induce tarnishing was suggested too.

What does oppo think?