At first I couldn't find this online as most people call it a "screen door brace", but that only turned up one obsolete item. Found this by scrolling through screen door accessories.
This is a well-made screen door brace. Not that they are hard to make, but clearly it was made by people who care. Installation was trivial and I didn't even need a wrench to turn the turnbuckle. Now my tired man door closes smoothly. I'll get another decade out of it yet.
Worth noting is that the other store who's name rhymes with "Moe's" doesn't carry any screen door braces at all. But one I found it online here, Home Depot told me the local store had it in-stock and exactly where to find it. And the information was correct!
Bought this to prevent sag in the screen doors that I purchased. As happens with all wooden screen doors the ones that I installed were starting to sag with more use. Installed the turnbuckle and it eliminated the sag and allows the screen door to open and close without dragging.