Piezoelectric Crystal. (Please Assist)

Hi to all , i'm a ME student doing my final year project, working on
piezoelectric crystals. My plan is to produce enough electricity to
charge up a  AA battery when in motion ,  using the piezoelectric
crystals method. But i'm unable to purchase any or able to find any
one yet. Is there any specific ones that u all can suggest? any place
i could purchase it ? or even suggestions to help in my project ?