This is a CP that I found on FW and looks pretty good since its back and its the lowest price around.

http://www.amazon.com/Xbox-360-Wirel...apter-Networks...
Retail List Price: $69.99
Current Sale Price: $53.99 + (Shipping)
You Save: $16.00 (23%)

After Price Comparison.....Amazon is still the Cheapest...see below for references

GameStop.com sells them for $79.99 + (Shipping)
http://www.gamestop.com/xbox-360/acc...360-wireless-n...

toysrus.com sells the for $79.99 + (Shipping)
Wireless WiFi Network Adaptor for Xbox 360 - Microsoft - Toys "R" Us