Leaking Engine oil filler cap using BMW seal replacement

[yellowelan]

Mine is leaking badly and I don't have local lotus parts seller. I took a punt on the CPC auto component oil filler cap OC55 from local car accessory store:

http://www.cpcauto.com.au/oil_caps.aspx

I had to buy the cap just for the seal. According to the site it fits old BMWs. It is slightly thicker and wider than the original. Snug fit in the twin cam cap without modification and seems to seal better than the original. So if you have the same problem maybe go for BMW parts dealer.