This is the easiest Instructable you will ever do. I purchased my materials for less than $50, but you can find them for free or almost free at garage sales and junkyards.
1. One trumpet mouthpiece. I selected the Belmonte 7c $19.99, as it is the most inexpensive around. If you want to add some color, Kelly Mouthpieces makes Lexan transparent mouthpieces in many colors and they are less than $20 on-line.http://www.music123.com/Kelly-Mouthpieces-Trumpet-7C-Mouthpiece-i121232.music
Also available on eBay and at garage sales.
2. 10' of copper coolant tubing 1/2 inch OD (outside diameter) $19.99. This will fit the trumpet mouthpiece perfectly. Available at any hardware store.
3. One Plews LubriMatic Utility Funnel $4.95. A galvanized metal funnel for oil and hydraulic fluid. The metal carries the harmonic resonance better than polypropylene, has a gooseneck for visual effect, and, coincidentally, fits over the copper tubing perfectly. I bought this at Home Depot in the hardware department.