There's always something like this:

http://www.amazon.com/Velleman-K1803-Microphone-Preamp-Kit/dp/B0002Z82XU

The cheapest and easiest boost-mode regulators I know of (that are also tiny) come from Pololu:

https://www.pololu.com/product/2117

I don't know if you're gonna end up with noise using a switcher on the above preamp, but it's worth experimenting with.