From any manufacturer who has a brass chimney on one of their instruments. In our shop we have taken 1" OAL X 1" OD solid brass stock, shaped the end concavely using a bench grinder(with a small wheel) and drilled the center out in our lathe using a 1/2" bit. This will leave each side wall with a thickness of 1/8". Or you can use it solid w/o drilling. We also take down the outside wall diameter (OD) and face the other end flat (now the top of the chimney), to proper height, as required by the set-up, in our lathe if needed. fwiw - this is not a DIY job unless you have maching capabilities, in most instances.shmuelyosef said:Where does one get such a 'brass chimney'...i have made them before out of brass tubing stock, but it takes a while with makeshift sanders and files.