do you want external anteni?
http://www.overclockers.co.uk/showproduct.php?prodid=NW-057-TP&groupid=46&catid=1597&subcat=1622
If you don't have a need for wireless N and can cope with wireless G, I have a lot of spare D-Link DWL-G520 cards sat around, free to a good home if you want one. Like I said, they're only G so will squirt 54Mbps tops