Hi and welcome.

First of all: if you mention your location, it might be easier to guide you to a shop.....

Secondly: I have used these polaroids for many years, and I have never used sodium-sulfite to wash the negatives....

(I leave the negatives in water for a couple of hours - then I gently wash the developing residue of the negative under running water, using the palm of my hand to clean it with - then I fix in normal fix - wash and dry. I know it is not what the recipie says, but it works like a charm for me - never had any problems with it...)

Again: welcome to APUG from Denmark.