I have no idea if this will suit your purposes exactly, but I will give a big hooray to the Olympus Digital Voice Recorder WS-300M. It's small and light and does everything I want it to do, and it's not too expensive. You can find it or similar models (it's about a year old now, so I'm sure you can get one with a little more space/bang for the buck) on Amazon.com and at Best Buy.

Hope this helps.