I just wanted to drop in for a second. Having come from the high powered rocketry world, there are a number of devices made to locate Rockets that are very loud and may be able to be adapted for this use. I just wanted to throw another option on the table.
I think they make them so loud becasue of the nature of the sport. Often times you are traveling a mile to find something 5 feet long and 4 inches in diameter that has just come down from about 6,000 feet. You may know it's in the cornfield, but which cornfield.
Tom