Best Buy offers the Microsoft Sculpt Comfort Bluetooth Mouse, model no. H3S-00003, for $19.99 with free shipping. (Amazon charges the same with free shipping for Prime members.) That's $2 below our mention from last summer and the lowest total price we could find by $3. It features BlueTrack technology and works on a range of surfaces and 4-way vertical and horizontal scrolling. It requires two AA batteries (included).