Take a look at the post of December 10th. The 7th Circuit is posting audio files of oral arguments (as are some other Circuit Courts).
If you want a transcript of an oral argument you might want to try the United States Supreme Court website page that links to transcripts of recent arguments before the USSC. These are now available within a day or two of the argument.
Consider this - attorneys appearing before the USSC prepare those arguments carefully. These transcripts are a record of some of the finest appellate advocacy available anywhere.