I also have a similar problem. Left foot is 12mm larger. That's almost 1.5 sizes.
In the past month, I tried over 50 different models. So I've already given up.
Today at Pohodnik all trekking models from Meindl.
My right foot is obviously very weird, as most shoes slip at the heel or lift at the heel by about 0.5cm when walking, if you add an insole, the shoe usually presses in the instep area.