What's the cheapest and quickest way to get wireless on my 3-year-old Mac laptop?

I’m the Bay Area, have no time to research this, and want a super cheap deal. I plan to buy a new laptop soon, but this upgrade is urgent (as in, I need it within a couple days). I have the white, 12-inch, OS 10.3.9, bottom-of-the-line in june 2004, no built-in wireless one….. I don’t have it in front of me – tell me if you need more details. Thanks!