You can see if there are any companies near you that offer aluminum vapor deposition, but it will be expensive.
I have had good luck with a product I found building scale models as a kid, 30 years ago... ugh, it pains me to say that. Anyway, it's called "Bare Metal Foil" and it's an extremely thin adhesive backed metal foil that comes in different varieties. It's fairly easy to work with once you get the hang of it and will reflect and diffuse better than paint. Obviously you don't need a mirrored surface, but if you so desired, you can even (carefully) polish these foils with metal polish to get an even more reflective surface.
There don't seem to be too many hobby shops around any more, so I suppose you'll need to buy it direct if you can't find any on Amazon... so here's their website:
Bare-Metal® Foil is perfect for duplicating chrome on model cars, model trucks, and model aircraft. Bare-Metal® also looks great on die cast models. You can use Bare-Metal® any place that real metal would add detail to a finished kit. Bare-Metal® Foil is a thin metal foil with a self-adhesive...
www.bare-metal.com