try
swift tools and click on SwiftMP3 - its partly what we used to develop the mp3 player we made in the last company I worked for - the
Cleoplayer is probably you're best bet if you just wanna use someone elses fla and modify... saying that the player above linked to by pixelpyro looks alot better I'd pay the small fee and use that personally - it looks and works a bit like the one we developed - have a look I've used it a few of my clients sites - see
www.menschmsuic.net for a good example - (I over did the mp3 compression but if u want it to stream on a 56k u got to really...)
both the software for converting mp3's to swf and the cleoplayer fla are free, so go experiment!
I have an older version of the actual swiftmp3 converter that runs with windowz 98 if u need it - they dont seem to offer that any more...