Testors Enamel Paint Marker-Metallic Gold. Currently $7.91 with Amazon Prime.

Seriously, my process was literally taking the pen and "painting" the grommets. B/c of the pen form factor, it's really more like writing. And the paint comes out very precisely, so I didn't really have any near-accidents. I didn't tape anything b/c due to the small and round nature of the eyelets, it would have been tough to do. And, I figured if I did get paint on the leather, I could remove it pretty quickly before it dried.

If you zoom in on the imgur photo, you can kinda see where I didn't quite paint the entire grommet on the third one from the bottom. Also you can see that the finish isn't super smooth, but I don't think you or anyone else would ever notice it without an up-close inspection.