Hi Stella,
I am not sure about any whitening spray, but as I keep a very-white-head-to-tail cat, my vet suggest me this whitening shampoo. I used it for almost a year and seems that it not give bad effect on my cat. Maybe you can try this brand? It smell great too.
Btw, it stated that
"Tearless, coat-brightening Bio-Groom Super White Shampoo makes white coats sparkle without bleaching. Designed to enhance white and light-colored coats, the rich formula cleans thoroughly while adding luster and body to coats. Controls matting and leaves hair smooth, manageable and shiny. Bio-Groom Super White Shampoo is fortified with protein and leaves a fresh, clean scent."
... Hope it would not give you any worry.
p/s: Sorry, pls ignore the medicated shampoo, it is for fungal problem. hoho.