I have a pair of - what I believe to be - original sun visors on my TR4-A. I think they were white or cream originally (any help?). Unfortunately, mine are now quite yellow, though in excellent condition (no rips tears, dents, etc). But I'd like them brighter. I have thought about light bleach on a cloth or sponge, then wiping off after a period of time. I welcome any better suggestions, as the replacements seem to be either all black or spongy white.