Lenovo offers its Lenovo N60 Wireless Mouse in Gray, model no. 0B71264, for $19.99. Coupon code "USP1AP531264" cuts it to $7.99. With free shipping, that's the lowest total price we could find by $8 (outside of the mention below), although we saw it for a buck less a month ago. This 3-button mouse features a 1,000 dpi resolution and 33-foot range. Coupon expires April 23.
A close price: Dig Jungle via Rakuten has it for $9.89 with free shipping.