You might be interested in this topic from a few year ago, where the audio description audio tracks were discussed:
Harmy's Despecialized Edition had just about every audio option you could dream of, although not all lossless - could you download the MKV and extract the audio files? There is also a torrent on MySpleen titled "Star Wars Laser Disc Audio Archive" which contains the 1977, 1985, 1993 mixes and the laserdisc commentary.