A ritual cauldron is, in material terms, ordinary cast iron cookware, the same three legged pot that stood in hearths across Europe for centuries to cook whatever the household could afford, long before any Wiccan or modern Pagan ritual repurposed it.
Makers, then and now
Historically a cauldron came from a general iron foundry or a local blacksmith rather than any specialist ritual maker, and the three legged design served a practical purpose, stability when set directly over open coals. Today, purpose made ritual cauldrons are sold by pagan supply retailers and by small craft foundries, typically smaller and lighter than a genuine cooking vessel since they are meant to hold a candle, water or burning herbs rather than a meal, and cast iron cookware bought from an ordinary kitchen shop serves the purpose just as well.
Care and no restriction on ownership
Cast iron requires seasoning to keep it from rusting, the same maintenance any cook applies to a cast iron pan, and there is no consecration or restriction attached to owning or using one, unlike several of the objects in this list. The legendary cauldrons of Celtic myth, Cerridwen's cauldron of inspiration and the Dagda's cauldron of plenty, lend the object its symbolic weight, but the physical pot on a modern altar is functionally the same iron vessel a farmhouse kitchen would have used for stew.