There are a few disadvantages to the new design: The sound is a bit weak, and the bright LED only allows for around 5 minutes of continuous soniking with each charge. Also, be warned that supercaps are known to not hold a charge well, so don't expect it to work after leaving it lying around.
That said, you will need:
a magic marker,
and a mini-usb port (mine broke so I went with the audio jack and rigged a custom charger).
The new stuff!
A pair of supercaps
! these will be in series for a nice 5v, which is also what USB provides.
Basically, it's a pair of conjoined 555's.
I found some cheap ones at that link.
An earbud speaker, or similar small noisy device.
Some capacitors and resistors; capacitors are 10, 0.1, and 0.01 uf. resistors will vary.
scissors, craft knife, pliers,superglue, a drill, and soldering stuff.