One idea would be to make a small cover plate out of stainless steel strip material to bridge the gap. This was done sometimes where a large left and right side molding come together in the center of the body.
Couldn't find anyone parting out a '62 LeSabre or Wildcat 2-door. If you have to keep looking, the Buick part no is 1360190. Left and right molding are the same part. Only used on '62 LeSabre 2-Dr sedan, hardtop, convertible, and Wildcat hardtop.
What has been, can be again. (Bob Wills, 1942)