The Frontier Labs NEX II or NEX Ia might be what you are looking for. I use the NEX II with lots of success. It's tough, well built, takes AA Batteries and read CF Cards or Microdrives. And the sound is excellent too.
They can be had anywhere from 40 Dollars up on Ebay.
Does anyone know of a larger capacity MP3 player that uses either AA or AAA batteries?
Specifically, I'm looking for either a 1 gig flash drive with an SD card slot (I've already looked at the Sandisk Sansa e100; doesn't seem to be a good fit for me), or a 4+ gig micro or hard drive player. The only hard-drive based players I've seen use built-in batteries, which don't do a lot of good when you're backpacking (I've also seen the Creative series with a user-replacable battery, but plunking down $30 for an additional 12 hours isn't an option either when you're talking about 1-2 week trips).
I'm not overly concerned with any other features, but ideally I'd like drag-and-drop transfer support, native playlist support, FM radio, line-in recording, etc, pretty much in that order of importance.
Any help would be much appreciated. Thanks.