The Allegro SLA7062 IC's can be purchased from:
formatting link
They have plenty in stock for immediate shipment. (707) 448-375
Also available is a PC board for the SLA7062M and a kit to build complete unipolar microstepper driver using this IC. The kit ha optoisolated inputs and a idle current reduction feature that reduce the motor current by 50% when the drive has not received step pulse after a 2 second delay
formatting link