Mwave offers the Viotek 2.4GHz Wireless Mouse and Keyboard, model no. VT-KW-10C, for $21.99 with free shipping. That's the lowest total price we could find by $3. The mouse features up to 2000 dpi tracking; the keyboard is waterproof.
Update: As a reader found, Better Choice Online via Amazon offers it for $19.99 with free shipping.