If its of some assistance, you are looking for a Multibeam #915419.
You should also contact Roy Judd who is also on the vendor list. I purchased a pair of his masterfully reproduced units for my 32′ and they are pieces or art and marvels of modern material science. Sitting side by side, its difficult to tell his pieces from the original glass. He’s retired, so once his stock is gone, that’s it, he’s not making more. 100 years from now people will be handling his lenses, wondering "where did these come from?" 1000 years from now beings from another galaxy will land on earth, and wonder what the 2 clear prismatic disks are laying in from of the pile of iron powder.
If Dox Axelrod and Roy can’t help, add "Multibeam Headlight Lense Lens" to your favorite searches list on ebay. If all else fails I have a pair of 33 Buick Multibeam 91522 and 915230 right left pair that I understand are suitable substitutes to your application.