I'm sure you could look at craft or fabric stores for metallic screenprinting paint.
I once tried using a metallic sharpie. it looked great for a while but eventually lost all it's metallic quality. But GF is right about metallic fabric paint and that works well and doesn't fade as quickly
There are silver, gold, and other colors of fabric paints. Check your local craft store. They can be applied manualy, or possibly used in a screen-printing process.
Metalic-colored threads are available for embroidery as well.