After due consideration I think I'll be settling on an electronic plastic one. There's a few currently doing the rounds (one it a fetching curious orange) which seems ideal in terms of portability & tuneability - essential when I'm using my old simple system military (?) pitch C & Bb clarinets, pocket trumpet and a variety of otherwise untuned gew-gaws (Jew's Harps) & overtone flutes.

Meanwhile, I'll be making do with the stylophone...