Jason, if you really need one real bad, you can use the Fiat or Lancia oil cap. They are the same except their not chrome.
Any of the Fiat model like the Spiders 1.4, 1.6, 1.8, and 2.0 Litr. engine, all X1/9 models. As for the Lancia"s, all twin cam and Betas model 1975-1982 Yugo uses the same oil cap as well. I use to get my cap at the wrecking yard for like $1.00 I hope this help.