Franklin eBookman 901 8mb PDA
asking $60 shipped

It supports mp3 playback and has a memory slot on the back for MMC memory cards up to 64mb according to the website (others have had success with 128mb MMC cards)
here is a link to specs on it.
It has a bigger screen than most PDA and the unit is roughly the same size as most.
It allows voice recording and can read some audio ebooks to you.
I will include a leather carrying case for it too