Having spent some of my early years at sea for extended periods, often in locales in which there were no friendly, convenient refrigerated stores ships in the neighborhood, I foreswore ever again partaking of powdered eggs and powdered milk, unless they were unidentifiable components in baked goods.

Were I searching for powdered eggs in modest quantities, after Amazon which sells everything, I would look to local/area restaurant suppliers (most of which discourage "retail" sales), the bakery at a large supermarket which might sell me some, or to a friendly restaurant owner willing to buy from Sysco, etc. and resell to me.