Also what is shown above shows it like it is the bottom clip. That's because at the time I didn't realize there were two different clips. That is actually the top clip. The bottom clip is somewhat similar, except that it has more of a "block" of plastic at the bottom that keeps the screen frame from sinking down in its place.
Here is a drawing showing roughly how the straws go in (sorry, I should have used the same colors but I didn't).
In the drawing above, the blue is the metal track that is actually the main window frame as well. The yellow is the sliding window glass in its frame. The green is a representation of a plastic track that the window rides in. The black is the screen frame. And the red is the slit straw.
The original clips did three things: Hold the screen in place up/down; hold the screen in from falling out into the room; and keep the screen separated from the window glass by holding it off from the plastic track (see original annotated photo above). The straws do most of that reasonably well. There is no problem with repeated opening and closing of the window. I don't think they would hold up well to repeated sliding open/closed of the screen; but to my mind that's a secondary function -- opening and closing the window and having a screen there is primary.
So, what I did was remove the screen/frame. I then took five sections of cut straw and pinched them between my fingers them such that the two cut sides were together on one side, and thus the bottom of the "U" was on the other side in the center of the flattened straw. I then forced the "U's" up into the groove in the screen track (three straw sections on top, two on the bottom). The fact that they were once round makes them stay in by tension.
Now time to put the screen frame with the straws into the window frame. I started with either the top or the bottom (forget which now), and spread the "wings" of the straws so one would be outside and one inside (so they straddle the "fin" as in the drawing). Then I use a bit of persuasion (being careful not to bend the screen frame permanently) to do the other set of clips. Et, voilà! Screens in place
If you press downward, the straws will give and allow the screen to go downward a bit more than would be idea. But if you don't, they won't. And if the bottom clips turn out to be obtainable, then that would be even better (combined with the straws).
Also, maybe Retired Tim's hose method solves the problem better (?). The straws do allow limited sliding of the screen (like to let a fly out).
Next a few photos with them in place.
