Also consider looking at Patrick (Gadjet) Gainer's past posts on phenidone and vitamin C and TEA. Getting TEA may be a challenge in th EU though.

They don't need to be long lasting in working form, because they are kind of like an HC 110 film developer syrup , but are a paper developer syrup also.

I mixed it up a few years ago, and used it first on film - nice looking negs- and then varriedthe alkalinity and used almost the same stuff to devlop prints