This part is the top of the brew/grinder basket. It contains the beans during the grinding process, and also is critical to the brewing process because the water runs over it and through holes above the coffee. It must be able to withstand the extreme heat of brewing, so there really is no homemade substitute. I have had two of these coffee makers for about 25 years and I love them! It was a great product. There were two models...one with manual buttons, and another with digital controls. I have the digital model.