Found this in the CD-Writing howto at http://www.linuxdoc.org/HOWTO/CD-Writing-HOWTO-4.html
You must have an 1.44 MB bootable floppy-disk. Create an exact image of this floppy-disk by issuing the command
dd if=/dev/fd0 of=boot.img bs=18k
Place this floppy image into the directory holding the collection of your files (or into a subdirectory of it, just as you like). Tell mkisofs about this file with the option '-b' and also use '-c'. For details read the file README.eltorito in the mkisofs-distribution.
Hope this points you in the correct direction. I have been meaning to give it a go myself and would interested to know how you get on.