As Sandy said, if you can't use it before it spoils, mix it in propylene glycol instead of water. All you need is the phenidone and the catechol. The bisulphite is for preservation. Glycol does that. If you think you need sulphite for some other reason, add a little to the working solution or to the B solution. Don't use very much, or you will lose the stain. Phenidone and catechol with sulphite and alkali is not much different from an ordinary PQ developer. The working solution should have no more than about 1 gram for every gram of catechol. That much will assure the superaditivity of the catechol with the Phenidone.
I find I can get good stain and tanning as well as good film speed without any sulphite.