Piezoelectric devices are among the most efficient and reliable solutions for power harvesting from environment vibrations. Considerable effort has been devoted recently in the engineering community towards reducing the size and increasing the power density of these generators at the micro level. The objectives of this paper are to identify commercially available materials and to determine the geometrical configuration best suited for energy harvesting applications by assessing their performance when used in a cantilever beam micro-generator with a fixed volume. To achieve this objective, a comprehensive database with properties of commercially available piezoelectric materials is first established. Then electro-mechanical simulation is carried out to study the changes in device performance with respect to variations in the geometrical configuration for a vibrating beam with a fixed end and a mass attached at the free tip. Once the materials and geometrical configuration providing the highest power output are identified, other aspects important to system implementation are discussed such as feasibility of fabrication at the desired scale and integration with the electronic circuitry. The results obtained provide guidelines for designing and realizing reduced scale cantilever-beam piezoelectric harvesters employing high performance, commercially available materials.