You can get piezo's from any basic electronics store. Iuno where u are, but here we got **** Smith's, Altronics, Farnell, Tandy, etc etc.
If you find an old pc you can just take the speaker from that, FREE!!
"As a result of all this hardship, dirt, thirst, and wombats, you would expect Australians to be a sour lot. Instead, they are genial, jolly, cheerful, and always willing to share a kind word with a stranger, unless they are an American." -- Douglas Adams