engine oil cap gasket substitute?

Hey folks. I have a 2003 sprinter. the engine oil cap seems to have a gasket under it, mine must have fallen off. I see oil leaking around cap. I ordered gasket from dealer, but until it comes, some oil splashes out. Is there a safe material to use to make my own or should i wait till get part. rubber i think will melt
Thanks
Joe

Any decent auto parts store will have sheets of oil/heat/gasoline-resistant neopreme which you can cut/shape with scissors and knives.
(they'll also have many pre-shaped gaskets),
They won't melt.

Just ask for "gasket material"

--dick