MiniInTheBox offers the Brelong Motion Activated Toilet Light for $14.99. Coupon code "121LED" drops it to $8.99. With free shipping, that's the lowest total price we could find by about a buck. It features UV lights and requires three AAA batteries (not included). Deal ends January 16.
Note: This item ships from China and may take two to five weeks to arrive. Uncheck "Add Shipping Insurance to your order" during checkout to remove the 49-cent fee.