I had some soft and supportive insoles made by my podiatrist

Perhaps you can have a pair of boots made for you? While yes they will be expensive, it's likely they can be maintained and rebuilt as needed.

Good job. Everyone has unusual situations they have to deal with.

Back in the 60s my mother happened to have a pair of shoes that she never wore because they were too small. It turned out that a Hopi neighbor's father in Tuba City was shoeless at the time because he couldn't find any pair small enough to fit him.
My mother's shoes fit perfectly, so she gave them to the man.

Weeks later we'd pretty much forgotten about the whole thing when the man and his son showed up at the door with a hand carved Kachina doll to say thanks. My mother kept the, ultimately worth hundreds of dollars, Kachina until she died.
It's amazing how doing relatively small things well can make very large differences to people.

May be easier to just gain weight so your feet get bigger...

My wife has narrow feet, kind of funny watching her try on a pair of Blundstones, they just fall off her feet when she tries to walk.

oh sorry don't know how I missed it. Beautiful boots. I use orthotics from my chiropractor that are exactly my feet. Supports my arch and does make less space inside. You could see iif orthotics help. Or good quality insoles.

Disappointed no picture, but clever idea for sure. Hope it keeps keeping your feet in. I don't have narrow feet, but more often shoes feel too wide. I have a high arch, so have to try kn every shoe that it gives me space.

Nope big wide feet size 13 double E

Good job finding a creative and cheap solution!!