This is a very good, simple circuit.
It would easily fit into an Altoids tin.
Many years ago, a friend and I bought a half dozen microwave oven
beepers at a hamfest for a dollar.
I used one of them in just a continuity circuit. That is the beeper, a
9 volt battery, and clip leads that are part of the negative lead going
to the battery.
I never thought about the switch option Butch described.
I may just have to make that modification.
--
Mike Duke, K5XU