I have the aluminium ones, never knew they were an optional extra! I like them so they're not for sale i'm afraid, even if they do look a bit like they're from an audi tt. I'll prise one out on the off-chance they've got a part number stamped in the back.
maybe try emailing a Nissan dealer in Oz. I believe they were on the last of the run here. The cars were labelled a GT and is was basically Nissan getting rid of all the little extras they had left over..