Good luck with that, I did contact Prodrive quiet a few years back and drew a blank on the covers.
Seem to remember I also posted up an opportunity to gets some made up, either by Prodrive or get some cloned by a.n.other if the right numbers where there, nut again not enough interest.
Is it worth trying to sort out a cloned one again ?
What sort of prices was we talking Chris ?
I'll give it a try with prodrive but as said, i'm probably pishing in the wind 
I cant remember now if Im honest, twas about 6 / 7 years ago, the proper way was to get them injection moulded, biggest cost would have been the Tooling followed by x amount of pennies dependant on quantity per item, bonus would have been that I or We could have ended up with thousands of them, not sure if the market is or was big enough.
The other option was I did get in touch with someone who reckoned he could clone them by making a Fibre Glass mould then cloning them in some sort Fibre Resin, upside was could be viable for just a few handful of items, downside was cost per item as this is a fiddly handmade per item, honestly cant remember the cost now, but was viable for the right numbers.
As it was sometime ago I'd probably have to look into it fresh again, but as said all down to number interests.