Hobby Tool Supply via Amazon offers its Amazon prime members the SE Wireless Motion Sensor Light, model no. FL8403-10, for
$8.32 Update: It has since fallen to $8.17 with free shipping. (Non-members can spend $25 or more to qualify for free shipping; otherwise, shipping costs $5.14.) That's the lowest total price we could find by $4, although we saw it for $1 less in January. It uses infrared technology to sense both motion and heat and features 10 LEDs. It operates on three AA batteries (not included).
Wireless Motion Sensor Light 10 Super-bright Led Tools & Home Improvement is also available at these stores