Klaus2008's idea is to make a new bootable USB, including providing persisent storage,
exactly the same way as the first was made. Presumably from a CD. The only difference
between the two USBs should be the persistent images. You then cut-and-paste with
the USB's unmounted. You erase the clone's new knoppix-data.img file and replace it
with a copy of the knoppix-data.img from the original USB. You can even do the cut-
and paste in Windows, as I did.