Cheaper way to build a wireless adapter in a Xbox phat?

[cobi_vw]

My friend recently asked me If I can install a wireless adapter into his Xbox phat. But, the adapter's really expensive. Is there a cheaper way to do this? I don't want to charge him like $50 for it. 

Heres the one I saw: http://www.ebay.com/itm/Wireless-Network-Adapter-For-Microsoft-Xbox-360-genuine-/320871157674?pt=AU_Components&hash=item4ab5694faa