Logitech M570 Wireless Trackball Mouse for $27.50. Shipping is free on orders over $35. If needed, use this Filler Tool to pad the order for free shipping. Here is a screenshot for your reference. The wireless trackball mouse includes a tiny wireless receiver and features an adjustable laser sensor, scroll wheel, and programmable buttons. Most places have the wireless trackball mouse for about $49.
This deal has expired as the price has been raised. Congratulations to those able to get in on it.