I own a Mac laptop

Question

I own a Mac laptop model#AppleM6497.My cable company TimeWarner has just set me up with RoadRunner and D-Link Rangebooster G Router.I would like to buy a D-Link USB Adapter Range Booster. My local OfficeMax store called your company and was told I needed WUA #1340 or#1440 .They did not have one, neither did my local Circuit City or Best Buy.Could you tell me please where I can obtain one? or send for one? I live in Winston Salem North Carolina