I have tried using USB stick before, but I always had issues with the drivers. It was very unreliable.
If I was you, I'd get a original airport card. I think you'd also need the adapter, but I'm not 100% sure.
The cards go for $ 20-30 on Ebay.
I have one left over from my iBook 3G (Dual USB) that recently died.
Send me a PM (private message) if you are interested, and tell me how much you're willing to pay.
-t