As other member have written above, your objective is unrealistic, because the frequency response range of ANY electret capsule is wider than that of any small speaker.
Measuring the frequency response of a microphone is not trivial, it requires a wide range speaker whose frequency response is known (surely not the one you are proposing), an anechoic chamber, suitable amplifiers (both for the speaker and the microphone) and a suitable meter or an audio analyzer.
I any case, what you are searching is a small power amplifier (a good audio transformer could do the job, but it will be an order of magnitude more expensive than the amplifier).
Search e-bay for "audio amplifier board" and add a simple power supply.
You can find a suitable one for some dollars.
Best regards