I have both white and black amplifiers, which the last one is the one I use. Like Mirax said before, the white one, while compact and works with a single 9V battery, it's just a hassle to work with.
The mic I use for it cost me almost an arm and a leg (almost $20) for the mic itself, Clip-on, Electret Condenser Microphone, Part # 33-3013, which works with a mini watch battery to power the little mic, and it works sometimes (bummer), and was the only single microphone that worked from the whole selection at the store (tested by the sales rep. there).
Bottom line...go for the black one instead, and you have the mic included.
Robert