Yep, they don't come up very ofte especially with the exposed carbon bonnet. Would imagine that spec is in single figures in the UK. Have you spoken to Richard Grace as he may know someone with one. Good luck with your search.
I also prefer the body colour match . When I was looking for my Centennial Grancabrio I messaged Maserati uk to ask how many had been sold in the uk. It’s single figures in both colours for the GC so suspect that GT similar.