For my roadster I recently purchased blade assemblies (stainless ’50s style blade with rubber) from Bob’s Automobilia who has them 10, 11, 12 inches. Believe I got the 10s. See this page: http://bobsautomobilia.com/shop/wiper-items/
Bob is the source of the ’40s-50s style stainless license frame that adjusts to the plate size. This accessory was sold by virtually all dealerships in those years.