For Prime members only, Amazon offers the Microsoft Arc Touch Bluetooth Wireless Mouse in Silver, model no. 7MP-00001, for $36.81 with free shipping. (B&H Photo Video and Jet.com offer it for the same price.) That's $2 under our March mention and the lowest total price we've seen. (It's the best now by $16.) It features a flexible design, touch scrolling, BlueTrack technology, and purportedly up to six months of battery life.