Cinch buckles from OnRope1
Seat belt webbing if you are a DIYer.
If you don't want to fuss with it, they'll do the loops for you. You can order a 30' and then cut it in half.
I have used whoopie slings and tree straps on all of my DIY hammocks and find them very easy to use and don't really understand all of the comments about "fiddle factor".
I just got a new WBBB with their style of strap and cinch buckle suspension. I truly wanted to like the suspension. However, so far I hate everything about the strap/cinch buckle suspension and think it is the system with way too much "fiddle factor" and difficulty of use with cold hands.
I love the hammock and hate the suspension. I will make whoopies and install them tomorrow.