I was just on a job this week and ran into this situation which I have dealt with before but used different things to hold the shades back from the window. But I did not have them with as they were in the other work truck. So I had to improvise something else and this what I used and now that I used them I like this way better as the ones I normally use are of plastic and heavier.
All it is, is the end of a film box cut to the length I wanted and then cut it down the middle and folded the sides together to make it more ridged and taped it down and as you can see it worked great plus if they fall out no chance of damaging the floor. Just thought I would share this.