Sometimes, extreme portability makes us do desperate things.

  # uname -a
  HP-UX prdcrm B.10.20 A 9000/800 862741461 two-user license

  # ls -l /dev/urandom
  /dev/urandom not found

  # openssl rand -base64 8
  v51U1RvSD2Q=

I could run this on VAX VMS if you want.