The other option is to fabricate one up using MDF, fleece and fiberglass just like the audio guys make up their sub boxes and custom door panels. A quick search on Youtube would give you an idea of how it's done. You just have to enjoy lots of sanding and fumes .
Maybe you could utilise the metal structure of the dash as the framework to build off.

However it should be noted that with either the custom alloy or fiberglass dash you don't have the factory foam type layer and potentially this could be a RWC issue not to mention a safety issue if your head happens to meet it.