.
Klaus K lists the mirrors for Knoppix at http://knopper.net/knoppix-mirrors/index-en.html, as Capricorny points out.
The DVD for 7.0.5 may be found at ftp://ftp.uni-kl.de/pub/linux/knoppix-dvd/, among other places.
I think it is true that Klaus K is, or was, a teaching professsor at uni-kl.de, so that's the site I usually use.