Hi Mark,
There's a chap called Thomas something who advertised stainless rails on FB, both top and bottom,
a while back but I haven't seen his posts for a while. He was also making fibreglass
seat backs and boot spoilers (similar style to yours).
Try searching on the Italian-based FB sites.
These rails are of critical dimension to fit well. I had my top rail repaired by a mate at work, but
he's no longer got the equipment to do it. A repair is often the better solution as it's more likely
to keep it's dimensions.
Nigel