I really liked the .40 trumpet posted elsewhere here. While not nearly as pretty, I have made a number of "trumpets" using empty shotgun shells from successful hunts. I just drill out the primers and insert a length of rigid copper tubing...then adjust the depth of the tubing til I get the sound I want...a rubber faucet washer completes the mouthpiece. Works for me!
Give it a try,
L-Wes