I bought an MPR and agree that they are better than the original Fly-O.
I went to a surplus store and bought about 20 surplus rolls of macrame cord for 60 cents each. I cut them into 20 ft lengths, and used a cigarette lighter to melt the ends so they don't unravel. They are for beginners in our TU class.
Your suggestion to use parachute cord is interesting. I'll try that once my macrame cord runs out.
I wrote Echo about a year ago and they will sell the MRP "line" for $10.