As one of its daily deals, MidnightBox offers the Wireless Sensor Bar for Nintendo Wii
for shipping. That's the lowest total price we could find by a buck (outside of the mentions below). This sensor bar allows you to upgrade your wired Wii sensor bar to a wireless replacement. Note: This is not a Nintendo-brand product. Deal ends today.
A close price: Hitgaming Video Games via Amazon and Monoprice via Amazon offer it to Prime members for $6.07 with free shipping.