Who would have thought -- now even these parts are being reproduced: The Parts Place Inc. has them, listed as: Body Panels - HOOD GRILLE PLATE (1969 - 1972 Skylark/GS/Regal/GN) GS RAM AIR HOOD PLATES (MOUNT UNDER HOOD TO SEAL TO AIR CLEANER) - PAIR Currently going for $99, although lately there have been a few of these on eBay along with the heavy metal external grilles.
Just looked them up Hood Grille Plate: https://www.thepartsplaceinc.com/NewProducts.aspx Hood Grille Bezel: https://www.thepartsplaceinc.com/NewProducts.aspx Hood Grilles Diecast: https://www.thepartsplaceinc.com/NewProducts.aspx Good to know...