1972 CT70H Headlight

Hello, just bought a CT70H U.S. model and wondered if anyone can advise. One of the filaments of the sealed beam headlight is kaput. The diameter of the lens is 115mm / 4 1/2" I've seen replacements sized at 4 3/4" and wondered if these will fit or if not, does anyone know of a suitable replacement lens. The headlamp is a seperate part, not the type with the inbuilt speedo. Thanks.