I've used reflective guy line in the past. Though not the Triptease type. It's been awhile but I think we stopped using it because the supplier no longer carried it. I don't think I've done a search for it in sometime. The Triptease cord is nice but extremely expensive, even in wholesale quantities.
I've got some of the Clamcleats and I've been looking for some cord that will work in both those and in tension buckle used on our tents. So far no luck on that score. It would be nice if it also had a reflective thread running through it.
Ron