Nigel, it's something which could easily be done by Superform and produced in good numbers. In fact some might argue that an aluminium tray should be standard. But they would sell well as aftermarket.
I've made one in wood and one in aluminium, and they are an absolute pig to get right with basic tools, so I doubt that anybody will hand craft them in numbers.
Nice to see that I've inspired at least one more though!
Thanks for posting the link.

DaveW
'05 Red Roadster S1
'16 Yellow (Not the only) Narrow AR GDI Plus 4