1st, my qualifications:
I've listened into and lurked around conversations of subjects like this, that I learn enough to assume that i know what i'm talking about. Anyway...
On my PC, I have a Creative Labs Audigy sound card and on the recording panel of this software, they have a function button, ARVL which stands for Auto Recording Volume Limiter.
I record mostly keyboard/instrument stuff, and not voice, but i find that it does work well for what i'm doing with it. One minor negative thing happens sometimes.
If the signal is too strong for a continuous length of time, a few seconds or longer, the limiter tends to overcompensate so on playback, that part of the recording is too soft for my liking. But as i said, i'm recording music where this issue is more of an impact in comparison to voice. I can still hear that part but there is a slight, noticeable drop in the volume.
I would think that other sound cards would (or should!) have a similar feature.
What about sending the mic into 1 of these small compessor/limiter/enhacer boxes that you find in the music stores, usually between 29 and 59 dollars? I've seen models of these that would easily fit into a laptop bag.