We have finally released our own custom 3SX Oil Cap - it's fully CHROME and designed to match the other underhood reservoir cap covers we offer! We designed it to have an seal that seats perfectly against the top lip of the valve cover where the cap goes to prevent oil leaks (check your valve cover to make sure it's not damaged!) and also with a thick and sturdy retaining tab to securely hold the cap in place and cinch down on the sealing oring, again to help prevent oil leaks.
These are made from billet aluminum and use a steel retaining plate to hold it against the valve cover.
This is designed specifically for the 3000GT/Stealth, but should fit most Mitsubishi engines using this clamp-type oil filler cap.
Note that these oil caps DO work with the stock oil cap gasket, so if yours dries out or gets damaged somehow, you can simply use the stock oil cap gasket.