These are details for a morse pratice oscillator made by my son Michael, 2E0REC, for his intermediate exam practical construction project.
The oscillator is a straightforward use of the NE555 oscillator chip. The Morse key simply gates the power feed, which causes a slight "chirp" in its frequency. The schematic came from M0DAD's website: http://www.delboyonline.co.uk/m0dad/construcion/morse_practice_oscillator.htm. The top right pin on the IC (which doesn't have a number as drawn) is pin 7.
Michael constructed his oscillator on 0.1" strip board. He has used a front panel volume control (sometimes I think headphones would be a better approach!) and used a preset resistor on the strip board for the tone setting; a front panel potentiometer as shown on M0DAD's site would be fine as well. Here is a file showing the strip board layout he used:
The finished unit fitted into a simple plastic case. I suspect this one came from Maplin, but there are many suppliers. Just about any small loudspeaker would be suitable, from an old dismantled radio for example. Again, suppliers like Maplin have many suitable speakers.