Hi Roly
I have a fibreglass bootlid for a Mk1, 2 or 3 for sale which looks ok from the outside.
I did find a scrap one at Spit Bitz but decided it needed too much repair - all rotted out at the lower edge as they all do.
Failing that you can buy a new steel one as I did from TRGB at vast expense, but if it's got to be right...…………………………………...