The Atari Times: Defender 2000 - Review includes screenshots. "Minter finally releases his second blast-a-thon." - http://www.ataritimes.com/article.php?showarticle=14
AtariAge: Defender 2000 - Contains scans of the game manual. - http://www.atariage.com/manual_thumbs.html?SoftwareID=2527