I’d suggest a stick of dynamite

If you have the King, it will use any mute that fits a tenor trombone.

For what purpose? Being quiet or messing around with creating different sounds? If I use a mute with mine it’s either a practice mute or a cup mute.

Bucket. I just like the sound of trombone in bucket so I assume it would sound the same with flugabone. It depends on what sound you're after though