So far the choices are juggling with the pendulum type metronomes which as I recall you need a level place to put them in order for them to work properly and to carry them around require another bag in your hands besides your trumpet, mutes, music stand, music, lunch, stereo tape/radio/CD player on your shoulder fully loaded with 8 – 10 C batteries for background music while you are playing.
The other choice is to have all of the above minus the "juggling pendulum type metronome" in a bag and in its place you have a computer with 19" screen with tubes (less costly) with a portable generator on wheels for electricity or a fully charged lap top strapped to your breaking back while walking with your buckling knees.
The other choice is to have none of the above but only a Boss Co. Dr. Beat metronome tucked in your shirt pocket with or without headphones to listen to that beat and if you do not want to carry it during use, there is a hole to fill with a pencil/pen to prop it up.
Liad