If it's still under warranty, they will provide you with a new one. If not, then you can purchase a replacement from SONIC|blue. Look for it under the Steals & Deals section of the SONIC|blue store online.

Someone else had also discovered who made these AC adapters and what model # they are, so that if need be you could purchase them from the manufacturer once SONIC|blue runs out. That information is posted in another thread which I can't seem to find at the moment.