I bought mine at Seattle's famous Uwajimaya store. You can find soy sauce fish at specialty food stores, Japanese gift shops or online. I am quite giddy over these briny gems.
The secret of the blue earrings is madly fun. With the cap removed, pinch a fish between thumb and forefinger, then dip the opening in paint. Release the pressure and suck up about a quarter of a fish's worth of color. Squoosh the paint around to cover the inside completely, and let it dry.
Now the color is sealed inside! Snip off the neck like so:
The color is up to you. Any paint should work - I'm agog to experiment some more. I really want try it with antique gold enamel, glitter paint and, ooh, neon coral!
Converting them into jewelry is easy peasy. The plastic is so soft, a thumbtack is enough to poke any holes you need. I made simple wire loops to add pearl 'bubbles,' and attached them to fishhook earwires.
The clear pendant was even simpler. I poked sideways holes on either side of the mouth, then inserted a big jump ring as a bail to attach the necklace.
Since these fish weigh nothing, I added a heavy crystal bead and some glass pearls to the fishtail for ballast. I found the prettiest fish clasp to finish it off.
You know you need this cuteness in your life. So find a Japanese gift shop - seize the carp - and make some jewelry!