The packages I am looking for were not downloaded as part of an upgrade, they were installed onto the CD image and there are no package files available. Many of the particular .deb files that Knoppix uses are not part of Debian unstable/testing, and so Knoppix uses .deb files put together by others. For example, the 4.3.0-0ds4 series of deb files were originally hosted at penguinppc.org (and apt was setup to point to this) - the author then decided to get rid of them because newer ones are now on debian.org in experimental. But now the originals are gone and you either must upgrade all of your X setup to 4.3.0-xxxx or you are stuck because you can't get to the packages Knoppix was made from. www.apt-get.org doesn't have anything either, the links are broken cos the author doesn't host them anymore.

If APT can't see the packages that were installed it will try to upgrade and break everything. I just spent four hours yesterday where APT decided to remove some packages and everything died. I've managed to get it reinstalled again but who knows how much stuff is busted now. Having a complete APT archive of all of Knoppix's packages would be nice, and it would also make upgrading to a new Knoppix release easier because you just point APT at it and upgrade away.