Not helpful (sorry Nick!) but I thought I'd mention that I use cheap tieclip mics (clip removed) as tiny harmonica mics that fit in my hand-cup, the lead trailing out between my fingers. They give me quite a good degree of control of my tone and I can still do the hand effects. I can plug them straight into an amp and the sound is every bit as good as I get from my much more expensive Microvox setup! The one I use most is the Vivanco mono one. Last time I bought one I think it was about £16.