Again, I no longer have a photo, but I actually made 2 of the things, the one in the earlier photo being the first one. They were easy to make, even for someone whose manual skills are as poor as mine.
The idea was basically 2 arms sticking rearward straight out behind the saddle at close to top-of-saddle height. The Nitto clamp, much better made, tho' essentially made the same way, by bending aluminum stock -- for some reason angles the arms downward. This is fine for Brooks-type saddles with the rails vertical in the rear, but on the rails of my beloved Flites it holds the bag needlessly low.
I got some sheet aluminum stock at the hardware store. I made a cardboard template of a squared-off "U", with arms cut so that, when bent at right angles, they stuck out straight instead of down.
I used the cardboard template to place the shape on the aluminum, and cut it to fit. I drilled holes in the bottom of the "U" for small U bolts to clamp it to the saddle rails, and then cut slots (in this earlier pictured version, just holes) for a front axle QR, onto which I slide a piece of small conduit pipe cut to fit between the arms. I attached the bag mounting straps to the pipe. The pipe let me clamp down hard on the QR to hold the bag securely in place.
This required no brazing, only work with hacksaw, Dremel, and files. It was secure, though the plate, to be workable with my tools and (lack of) skills was rather thin. But the arms were wide, and so securely clamped there was no sway -- indicating, perhaps, that it would last a while.
I recall that photo. This was a large grocery load, probably of 30 lb or so. No sway.
My brother has more skill and chose an easier way: He's made similar "clamp to modern saddle rails" QR saddle bag carriers using the dropouts of scavenged, trashed forks. But I think mine was more elegant.
I am very tempted to make another one for my present Medium Saddlesack, but as this bag is a backup used very occasionally, I haven't undertaken the job.