I made something similar for vehicle camping.
I took short piece of para-cord I had laying around and tied it into a loop. I had some clear plastic line like you use on ice makers. 3/8" I think? Cut the tubing into 1" lengths and slid them on the loop. Tied knot on each end so tubing can't fall off. You can slide the tubing to make whatever size loop you need for whatever your hanging.
I use a small bungee on one tree and more para- cord on the other tree. The bungee keeps tension on the loop. Key is the tubing must be snug on the loop, but still able to slide. I think you could use some leftover tent-pole bungee cord and that tubing and make a pretty good DIY imitation of it?