I won't address this generally, but just give you my experience.
I traveled from U.S. to Germany and back, and traveled around within Germany, with a Carol Brass pocket trumpet.
Carol Brass makes a pocket trumpet with a normal-sized bell so your mutes should fit it. I only took a Yamaha Silent Mute, which fits flush with the bell so I didn't need any extra space for it.
The taking up of space and the extra weight were negligeable. I put the horn, without a case, in my suitcase. It was well insulated and saved you the extra annoyance of carrying another piece of luggage around.
BTW, with the Carol, I never felt this was a compromise instrument, like using a plastic instrument, for example. It sounds and plays just fine on its own.