Try to find a Hummazoo.(Several different spellings.) They don't sound any different to ordinary kazoos when played openly, but they are circular, which makes it easier to vamp them like a mouth-organ.
Attaching trumpet-like extensions above the vibrating diaphragm also changes the sound. There's a metal one with a trumpet bit.

I once attended a workshop which offered prizes for the most effective kazoos. Strange things appeal to strange minds.

If you are around the English midlands, try to talk to Rod Felton of Coventry.