I have one of those Thetford porta-potty chemical toilets which I want to use for a few days but I don't have the chemicals. I was just reading an Australian caravan forum and most people use stuff called "Napisan". They say this is sodium percarbonate. Caravans are not popular here in Hungary so I'm unlikely to find specialist products but is there any laundry product such as Vanish that I could use to improvise the chemical toilet chemicals?