Lowes offers Square D X Series Single-pole 10 -Amp Occupancy Motion Sensor Light Switch for $9.50 (reg. $29.99) with free shipping. 

Product Description:
The Square D X Series 10A single-pole PIR Occupancy Sensor Light Control with back wires provides 180° occupancy sensing up to 1,200 square feet to make saving energy automated and easy. When movement is not detected, and the sensor times out, any movement within the next 30 seconds will turn the lights back ON. However, an independent light sensor will not turn on lights if ambient light in room is sufficient. Complete the look with one of the Square D X Series cover plates (not provided) that easily snaps into place for a modern, flush-facing finish to your walls. Enjoy a consistent look in your room or home with the full line of Square D X Series switches, dimmers, sensors, and receptacles.