I have been greatly enjoying this thread, and I would like to thank Stefan and everyone who cotributed by posting their projects and comments. On page seven of this thread Mark posted some photos of the inside of his microphone, and on that same page someone else posted a link to a piezo sensor similar to the one in Marks' microphone. I followed the link and ordered the sensor, installed it inside an old watch microphone I had and the results are better than I could have hoped.
IMG_0056 by Lavardo Forbes, on Flickr
IMG_0046 by Lavardo Forbes, on Flickr
IMG_0058 by Lavardo Forbes, on Flickr
IMG_0060 by Lavardo Forbes, on Flickr
IMG_0050 by Lavardo Forbes, on Flickr
IMG_0051 by Lavardo Forbes, on Flickr
IMG_0097 by Lavardo Forbes, on Flickr
IMG_0101 by Lavardo Forbes, on Flickr