Sorry, I forgot to add another option that we experimented with and that sounds closest to what you're describing.
We bought an Archos Jukebox Recorder 10 and almost everything about it worked well, USB interface, rechargeable AA batteries, external microphone jack, digital input and output and small size. The reason we switched to the minidisc recorders is that the interface for creating and managing the files on the Archos was a little too complicated to be able to put it into the hands of a reporter or photographer who didn't use it often and trust that they'd actually come back with something. That wouldn't be a problem if you used it a lot.
I'm not familiar with the current Archos models but the Recorder 10 and 20 machines are always for sale on ebay and at the prices they go for they're probably worth trying, even if you end up using them only as a USB back-up drive. There are probably other mp3 players out there with similar capabilities, I've heard the iRiver players recommended as recorders.
We bought an Archos Jukebox Recorder 10 and almost everything about it worked well, USB interface, rechargeable AA batteries, external microphone jack, digital input and output and small size. The reason we switched to the minidisc recorders is that the interface for creating and managing the files on the Archos was a little too complicated to be able to put it into the hands of a reporter or photographer who didn't use it often and trust that they'd actually come back with something. That wouldn't be a problem if you used it a lot.
I'm not familiar with the current Archos models but the Recorder 10 and 20 machines are always for sale on ebay and at the prices they go for they're probably worth trying, even if you end up using them only as a USB back-up drive. There are probably other mp3 players out there with similar capabilities, I've heard the iRiver players recommended as recorders.