Some microphone boards a gain control pot or you can change the gain resistors or build your own preamp.
Or, you can buy an audio mixer (they all have gain/level controls) and a microphone. Of course you'll have to bias the output. And, you'll need a regular stage/studio microphone. "Computer microphones" don't work with mixers or PA systems, etc.
I have one of [u]these[/u] and I agree. The sensitivity is a little low. For example, I have to crank-up the TV louder than I normally listen to get a "good signal". But there is some logic in that... It doesn't have variable gain so it can be overloaded (and clip/distort) and lower gain gives more headroom. Also, higher gain means more noise pickup/amplification (both electrical and acoustical)