Good one , Mike
I can add a little to that, if you don't mind.
The addition of another part, RS 275-1547, will aid in ease of use.
This is a momentary switch . [ miniture.]
Here is a wire diagram and also a pictoral .
Feel free to use this as a plan for your own and modify it to suit .
In the pic, you will notice I use a clear plastic test tube w/removeable lid. [ drug store].I mount the sw in the lid and exit the banana plug leads out
a hole in the bottom. I button it up with a right angle spark-plug boot for lead grommet. [ best to melt exit hole w/hot wire to prevent plastic cracking]
The unit can be assembled/soldered as a unit and then slid into the tube and pop on the lid.
The hand /thumb for switching is natural and makes for one handed operation.
This is second generation, so it has been tested out by some of the members and they have sent back favorable results. The first used a clear film can, but was cumbersum.