Gas cap replacement for 1972 ts250
 

I recently bought a 1972 ts250 off of a friend. The bike is in great shape but the gas cap leaks and it has stripped away the paint around it. He has tried resealing the cap but that didn't work. I am having a hard time locating a replacement cap online. Any help would be greatly appreciated
https://cimg3.ibsrv.net/gimg/suzukif...63905c4006.jpg