Get yourself a PAM 8043 off of ebay for around $5. Look for one that has a volume potentiometer and some visible capacitors on the board. It is a really nice IC for the price and does stereo. It's also usually on a very tiny board.
As for speakers, don't really know where to point you. I have so many extras laying around it just becomes a non issue. I do know that some people like to use DS lite or smartphone loudspeakers to save space. If you have some room I would look on digikey or amazon for a small set of real drivers. Or just tear up an old speaker dock or radio etc.