Okay, so I asked the expert – Bjarne Drews – and he says the embroidery is spangles and nothing else. And that it’s impossible to find metal spangles in black and white, which I’ve confirmed through some web searching.
So now the question is – use plastic sequins? Or switch the color to silver (or possibly gunmetal, if I could find that) so that I can use metal? I do think gunmetal would be a good compromise… Hmm.