Didn't lose it - the car is new to me and I believe the gas cap that I have is not the exact original and allows fumes to escape - trying to get a better cap ( non-vented I believe ).odd thing to lose.... did you leave it at the gas station and then drive off?
ask EB it it comes with a seal.....it will need the seal.
The original seal measures: 60mm OD; 50mm ID; 2mm thickness.
(you might find a suitable seal in one of the hardware stores)
or factory original seal on Ebay if you have a spare 30 bucks ()
ebay nr.: 193691835290