Amazon offers the Logitech Wireless Performance Mouse MX, model no. 910-001105, for $44.99 with free shipping. That's $5 under our September mention and the lowest total price we've seen for a new unit. (It's a current price low by $23.) It features four thumb buttons, scroll wheel, and Logitech unifying receiver dongle that allows the addition of a compatible wireless keyboard without multiple USB receivers.