Let's all agree that mixing Sodium Metabisulfite and Sodium Hydroxide is an expensive and inconvenient substitute for Sodium Sulfite, but once you've run out you are at the mercy of whoever supplies you and this can take a few days if not more.

Most developer recipes require substantially less than "pound quantities", therefore my substitute suggestion, with all its limitations as stated above, might work quite well for kb3lms. Depending on target pH and availability of pH metering device he might even get away with Sodium Metabisulfite and Sodium Carbonate in case he only has these.