I did use surgical tubing and it has worked well over the years, but the new stuff is much better. I was able to buy mine locally at a shop, but I recommend you go to Aerofoam Radio Control and look at their Hosemonster Bungees on line for the best as this is what I am buying from now on. They sell the Black, UV protected Bungee, so it doesn't dry out from the sun like mine does and they have a great price. Look for the "Catapult" section a page or so down and this is the one you want to get:

Standard bungee 1/4"ID x 1/8" wall x 25' with connectors $45.00 (shipping included Con.US. email for shipping elsewhere.)

It comes with the rings already attached and ready to go and is good from 28-35lbs of pull...pleanty for Minifan models like the FA-18 or even Midifan models later. the URL is http://www.aerofoam.com ...anymore questions, just let me know.

Carl