Bibs,
The part # you provided made an even bigger difference than I imagined; I gave it to my local dealer, who promised to check with Lotus USA. He called me back two days later and told me that I (more accurately, you) had accomplished something that Lotus themselves couldn't. He said that Lotus was chagrined and wanted to make up for it by sending me the cap for free. It arrived yesterday and is by all rights yours. I shall keep it safely attached to my fuel tank until you arrive.
2-Eleven forum is an invaluable resource. I upgraded my subscription this morning in appreciation of the help it has provided me on numerous occasions. At less than half the cost of the filler cap it's a real bargain.
Thanks again. And thanks to Lotus for being a company with a heart and a soul. They may miss the occasional part number but every time I have needed help, large or small, they have come through with support that was beyond my expectations. They build an amazing car and wear their enthusiast's heart on their sleeve,
Norm