Does anyone know of a site where I can download One Piece episodes?

Now, there is a thread in here about watching the episodes, but I don't want to do that. I want to download the episodes and put them on my mp3 player.

I've found some episodes, but they're in mp4 format, something I'd never heard of before. I can't play the files on my computer, and though I could no doubt download something to let me watch them, I know that no matter what I do, I won't be able to get the files on my mp3 player. I need avi or something similar (pretty much, no mkv or ogg).

I can't find any sites at all that have the early episodes in a format that I can put on my mp3 player. Can anyone help me?