Don't forget to shop around.
http://www.pcconnection.com/scripts/...ourceID=k15505
They have them for just $31.
Or if you want a more reliable business, amazon sells them I think. I remember last year we bought a couple more and for some reason I remember them being only $7, but I can't find anything cheaper than $31. Don't hold me to $7 - but maybe that's motivation for someone to find a cheaper price.