It's covered! I was spending too much time and energy looking for the best answer so I went back to the hardware store "saddles." Thanks to the input from commentors, I even tried making my own clips out of extra tubing, but couldn't get it to go over the cloche tubing. Big metal binder clips were a great idea too (so many uses) but they wanted to slide right off because of the plastic.
See how the saddles have ridges to hold them on, as well as the nice thumb spot for holding or removing them. I had also found an assortment of the bright clips, below. There are only 4 that will stay on the tubing, though. The others were too small. I'm using these 4 clips in the place that I'll open regularly. They are the easiest to remove.
The smaller clips work well to hold open or hold closed the ends of the cloche.
Lettuce, chard, chives, and two flowers are in there to see how they'll do.
Of course, we had quite a wind storm yesterday while I was gone. No movement to the structure but the plastic had blown around and some clips had come off. In the dark last night, I found enough to put the plastic back on. Tomorrow, I'll see how the plants held up.
21 hours ago