Hi I'm planning an experiment in which I will try to generate power from a force applied to some piezo electric material (in fact it will be an impact with the ground). I think I need to find a piezo stack, but where can I buy such a thing for a reasonable price? Does anyone have any ideas? (I'm not adverse to taking something apart to get hold of the stack) I've heard of piezo buzzers and loudspeakers, but do these use stacks? Any pointers would be much appreciated. Thanks.