Here’s the little pre-amp circuit used inside the mic:
The op-amp used is a microchip MCP6241, also not shown is a 5v power regulator for the circuit (not quite built yet) and the wiring for the jack plug and power switch (which are both fairly self explanatory, with the exception of the jack plug used as a switch to connect/disconnect ground to the circuit and thus act as a secondary on switch).
Here are a couple of photos of the mic with the electronics almost finished:
Will post a final set of details once the mic is totally finished.