Does anyone know where debian keeps the boot.img.gz files necessary for creating the stick?
By going to www.debian.org, clicking getting debian, scrolling down to "Tiny CDs, floppy disks, USB sticks, etc" then selecting your architecture, then clicking hd-media.
E.g. http://ftp.nl.debian.org/debian/dists/lenny/main/installer-i386/current/images/hd-media/