This may work. It's available in a flat finish.
My Dad used to have a paint that was used for marking trees from his job. It was a white, rough finish, just like a drumhead. I used it a couple times. It worked for making the head white again (but the sound was still dead from use).
It was probably similar stuff to the Ludwig Ruff Coat.
That was 20+ years ago, and before he retired, they started using different paint. Probably for the same reasons Ludwig discontinued the Ruff Coat. ALL the good stuff that worked well had lead in it, but it was really bad to breath it in in any amount, let alone years of being around it.
If you want to just keep a head looking new-ish, and help the coating last longer, you could try a workable fixative. You can get it from art stores. It's used to stop charcoal, pencil and pastel work from smearing after it's done, but you can still go over it.
It shouldn't affect the sound much at all.