err, none that I know of, maybe with a little bit of modification it could be possible, = also possible of hurting your H/U and/or MP3 player.

If you dont have aux input, might just try using tape adapter or a good wireless transmitter.

Although i am not too sure why you would want to keep it stock if you'd go so far as to wiring up the mp3 player, it'd look kinda ugly with wires coming out of weird places..

Get a good headunit, it'll sound better, more functionality, and you can probably get something that will work out much better than what you're trying to go for now.
In my opinion, (only my opinion) a silver colored aftermarket headunit in your eclipse will look very good.
As far as brands/makes/models/whatevers, its up to your tastes, research a few, look up whos sellign what in the for sale forum, go buy yourself something in the 100-150 dollar range if you're low on cash.