Useful sources of speakers are:
- Inside old Personal Computers. They usually also come with a wire and a Pin Strip connector attached, and look like the larger speaker in the picture above.
- Musical Christmas cards have a small piezoelectric speaker inside them that looks like the small gold disc above. This won't be very loud.
- Old headphones can also be a good source
Please bear in mind that Espruino can supply only 20mA at 3.3v on its outputs, so you shouldn't attach a huge speaker to it!