That's a meguyveer over to NAPA and buy a roll of gasket paper. Then it goes something like: taking the cap, place it on the paper, take a soft hammer and bang in the dent layouts across the cap. A straight edge razor and a cheap punch, then follow the imprint. Butter if you have that kind of vaseline on the item so more a press on the paper shadows out the gasket. Install cap, then razor cut what sticks out, because it's better to trim than too might induce a leak.
Not to takeaway from the jobbers here, but when the obsolete in paper is not present, there is always NAPA to the rescue. Ask me how I know.
