Kipp's apparatus with powders
According to the Wikipedia page on the Kipp's apparatus, if the reactant is a powder, and soluble in water, you can soak pieces of pumice in the solution, dry the pumice, and use it in a Kipp's apparatus. There is also a variant of the apparatus that allows two liquids to be used together rather than a liquid and a solid reactant. In that case, you would pre-dissolve the sodium sulfite in water.