Why do you think they are no longer available? Andover Norton still shows them available.
However, that's a great offer! Andover wants 20 pounds for one.
For anyone that just wants to do their own, get some air brake line from your local truck supply house. A diesel mechanic friend of mine has supplied me with free scraps left over from brake jobs at his dealership. I have been using my home made lines for 10 years.