Thats asking quite a lot. The only dictaphones (solid state or tape based) I've ever encountered were pretty rubbish with high volume and didn't last for anything like that long.
Its been a couple of years but I imagine what you're asking will cost serious bucks.
i think you're looking for high quality discreet component audio equipment matey.
minidisc perhaps?
Thought about this, whats the quality like and how do you get it from minidisk to pc?