Syah via Amazon offers the Anker Wireless Vertical Ergonomic Optical Mouse, model no. AK-98ANWVM-UBA, for $19.99. Coupon code "3UKHPA93" cuts it to $13.99. Plus, Prime members receive free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, shipping costs $8.28.) That's the lowest total in-stock price we could find by $11. It features a sensitivity adjustment button (800, 1,200, or 1,600 DPI); next page and last page side-buttons; and is compatible with Windows, Mac, and Linux. Two AAA batteries are required (not included).