I believe foma's kit is permanganate based.
Its really easy to mix yourself though. Chemicals are also not that difficult to find. You only need very small quantities of permanganate.
I have used it on photopaper, and it works well but goes bad after minutes so I use it one-shot only. Time and temperature is supposedly important when using it on film.
In additition to dichromate and permanganate, there is also copper-bleach and peroxide-bleach that supposedly works with reversal, but I havent tried those last two.