I took a 16 inch aluminum pizza pan, light weight not a cooking tray, and crimped the edges with my pipe crimpers and it fits the top of my diverter stone perfect. I have used this one now for weeks and it hold water for smoking like a champ.
A water pan stabilizes temperature fluctuations acting like a heat sink, catches drippings, and provides a moist environment for my meat. I believe moisture in meat is closely related to the amount of fat rendered. That being said, I have used a pizza pan and my trusty Costco foil pan with water, and both turned out great Que. I like the foil water pan because the drippings don't burn. Can't go wrong really. Love Kamado kooking.
Being relatively new to this type cooker, I have always used it for keeping the temps even. My vision Kamado is very good at heat retention, but I feel that the water radiates a more even heat across the grill. As the fuel below burns off in different spots the water pan absorbs the heat and evenly distributes it across the cook area. IMHOThe ceramic mass of the BGE does a great job of stabilizing temps so I've never seen the need to use a water pan. More mess to clean up.
But, that would make a nice drip pan to sit on top of the plate setter of on the lower grate of a two grate setup.
Being relatively new to this type cooker, I have always used it for keeping the temps even. My vision Kamado is very good at heat retention, but I feel that the water radiates a more even heat across the grill. As the fuel below burns off in different spots the water pan absorbs the heat and evenly distributes it across the cook area. IMHO
Well here you go. Your first look at a Vision Kamado Pro series IIIMakes sense. Maybe that's a difference between the Vision and the Egg. I've never even seen a Vision let alone cooked on one :-D