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.
I would go for gunmetal if you can find it. Silver, even if metal, I think will come across as plastic. You could always paint metal ones. It would probably take forever, but a coat of white/black nail polish would definitely do the trick. Doing a lot of drag queen and show costumes I use a lot of plastic spangles and such, and they just don’t hang the same as metal ones.
You might try experimenting with Pinata colors – I use them in crafty stuff for coloring things that never take other colors (plastics, weird fabrics, etc.) Their label says they work on metal grommets.
http://dharmatrading.com/html/eng/4302818-AA.shtml?lnav=paints.html
They sell the sets at a few places around town (Dick Blick for example) but I’ve never seen them sold individually except online. They are very very easy to use on plastics, not sure about metals.
If you find metal ones, you can make them black with gun bluing. I used this to turn silver studs black for a costume. Bonus is that to make them black, you can swish the whole lot of spangles in the solution, instead of painting them one by one.
Only problem is that it does make it flat.
if you really want metal, you could get silver plated paillettes from hedgehog handworks, and swish them in a weak belach solution until they get black enough (tarnished enough) for your liking.