Hello Trevor, We too have a Cobb and use Australian Heatbeads in it. Heatbeads used to be available everywhere from Tesco to Homebase, but for some reason haven't been available there for some time. We now get ours from a Garden Centre in Cold Overton near Melton Mowbray in Leicestershire but they are probably available elsewhere if you google it. The Cobb is a terrific bit of kit. Best wishes, butler.