cheaper version of andrews salts

Hi

andrews liver salts says on the packet magnesium sulpate, sodium hydrogen carbonate, citric acid.

At 5 pound a tub very expencive, is there a non branded cheaper version out there?

There used to be cheaper versions, but they seem to have all disappeared and I would like to know why this is.

I used to regularly buy Wilko own brand and also Superdrug, but the only one available now seems to be Andrews - it is definitely a mystery.