Get a running Alpha system with 'aboot' package installed and a loop device support (integral or as a module - does not matter). Here is how:

• create a directory on which you will mount, say /tmp/img
• mount this image like this:
  mount -o loop redhat-6.0.axp.iso /tmp/img
• type 'mount' to see which device is really used; probably /dev/loop0 but it maybe higher if 'loop' was in use before
• check ('ls') if 'bootlx' file is on the mounted image; probably it will be in /tmp/img/boot/bootlx but it does not matter where as long as it is somewhere; if nowhere in sight you are screwed and find another image somewhere else or make yourself one with 'mkisofs' - you have most files already in a filesystem just mounted - copy to a writable file system, clean TRANS.TBL files, add, recreate
• type
  isomarkboot /dev/loop0 boot/bootlx
  (use, of course, "real" loop device and bootlx location)
• umount /tmp/img ; rmdir /tmp/img
• you are done and you can blast that on a CD.