Billy can's are widely available in many varieties. My personal favorite is the Zebra billy can.
The billy cans themselves come in a variety of sizes with a strong and sturdy bail arm so they can be suspended over a fire. The billy cans come with a lid which speeds up boiling/cooking time and also keeps ash from going into your water/food. The billy can also comes with a steaming tray so as well as cooking/boiling you can steam foods.
Here is my 12cm Zebra billy can suspended over the fire boiling water.