There was a guy on the Dented Helmet that had made a few castings of a Jango Fett helmet in aluminum. In his thread he said he works in an industrial foundry, so a small casting like this is no big deal for him. He actually had his full costume assembled in aluminum and it looked pretty good polished up.
There was another member there who sold a few boba buckets made out of cold cast aluminum. This strikes me as the way to go.
Cold casting involves adding powdered metal to the resin on the outermost layer of the casting. When it comes out of the mold, all you have to do is scuff the resin off the surface and reveal the bare metal. Once you've done this, you've got a surface that's is identical in appearance to the actual bare metal only lighter in weight and non-conductive. The benefit is if you already have molds to make things in fiberglass or resin, you don't need any new technology.
So far I've done this using aluminum and bronze, but it can be done with any powdered metal. The drawback is, just like bare metal, it will tarnish or rust or patina or whatever happens when the real thing gets oxidized.
Here's a shot of a couple of my bronze castings using the cold cast method:
These were made using a water clear vinylester resin and a silicon mold. The most complex bit of machinery involved was a popsicle stick.