Valve Cover Oil Cap/Grommets

[gman]

My passenger side valve cover has on it an oil cap towards the front of the cover (the rear has the flame arrestor). Since the oil cap is a pretty sloppy fit......doesn't fit very tight......I was wondering if there is some type of grommet that could fit there that would seal up the hole in place of the oil cap? Or do they make oil caps similar to the one in the cover? The A/C compressor and mounting brackets sit right on top of that area so there is only an inch or so of room between the cover and brackets. And I do not want to replace the original valve covers for aftermarket. Any ideas what could be used? Thanks for any help.