Keim makes a Granital "special gold" paint which should be pretty
durable but is bronze powder product that could probably be used with
translucent glazes over, wiped clean on the highlights and varnished
to to give it sheen.  Lighting is also key to getting a good effect.
You could also consider cheaper, "dutch metal" leaf which also needs
to be varnished in order to keep it from darkening too fast.

The Rev Jim