I hope I am not violating any sales rules as these are a ebay sale item not auction.
There is a seller on ebay offering original Lucas boat navigation lamps for sale. These were used on original GT40's as identification lights that were fitted to the roof. These don't come up for sale that often so if you want one for your car I wouldn't wait too long. They are priced at £9.99 each and that includes the lamp fitting as well as lens.
I've no association with the seller but just thought I share the knowledge, oh and I bought 2 Clear lamps for sale Red lamps for sale