If it's just your horn you need to carry go with a single trumpet bag like a protec single trumpet bag. They also have a triple trumpet bag that has an awesome front pocket and plenty of inside space. It's called the ipac triple trumpet case.

http://www.amazon.com/ProTec-C238-Protec-Deluxe-Trumpet/dp/B0002D03ZC/ref=sr_1_1?ie=UTF8&qid=1377733666&sr=8-1&keywords=protec+trumpet+bag