I think the LeMans62 cars had aluminium boxes, but after that they were plastic. You'll get one on factory order but expect ££££££££.
It may be cheaper to have one made from aluminium.
(as I understand it)The LeMans62 was the first production car to have over-riders and the front number plate box is as Dave says Aluminium, it is certainly a piece of art as it combines as an under cowl that runs back to the cross member and attaches to the 'brackets' that hold the over-riders. A nicely engineered solution but I would imagine tricky to fabricate and no doubt V.Expensive!
How about de-cluttering all together and fit a 'stick on' number plate to the wing?
