Known for making Apple-oriented accessories, Macally has several new laptop mice specifically designed with Apple laptops in mind--although they're all standard USB peripherals, which will work fine on your Windows PC.
The $19.99 Macally Accuglide is a slim travel mouse, designed to be aesthetically compatible with the silver-hued MacBook Air. To say the $2,000 laptop and the $20 mouse look like a matched pair is a bit of a stretch, but the brushed metal top panel and mouse buttons (on a silver plastic body) gives it a fun, industrial-style look, as does the blocky rectangular design. With about the same footprint as a credit card, the Accuglide is 0.5 inch high, 2 inches wide, and 3.4 inches long, with a standard two-mouse button plus scroll wheel setup.
Being that thin, we could see the Accuglide easily slipping into a pants pocket or a particularly space-challenged laptop bag--an excellent characteristic for a travel mouse, even if the totally flat design doesn't seem particularly ergonomic for extended use.
However, we're not sure why anyone would want, even for only $20, a wired USB mouse. The cable neither detaches, winds up, or otherwise stores itself inside the mouse body, and for most users, it wouldn't be the best strategic use of the MacBook Air's single USB connection.