Well, I've had no luck in finding this chemical. Photographer's Formulary has a Potassium Hydroquinone Sulfonate in their catalog, which I believe may be same chemical. However, they are out of stock.

Is it possible to synthesize potassium hydroquinone monosulfate by combining hydroquinone with potassium sulfite? Alternatively, it is possible to make a sodium hydroquinone monosulfate by combining hydroquinone and sodium sulfite?