The vinylclad interior metal used in the 70's is no longer available.
The only source may be some used material from a wrecked coach.
However, because the vinyl can and does discolor from cooking with grease and oils, along with cigarette smoke, the replacement material you find may not match.
But, as an alternate, you can install Ozite or some other brand wall covering, to hide the problem.
Good luck with your search.