Slippers for men

are a vexed subject in our house.
The Senior Cat and slippers are a topic of frustration and despair.
For years he slopped and slipped around in the felt-with-rubber soles variety. His feet are about as flat as you can get - more like a duck than a human (or even a cat). If his eyesight had not precluded him from army service in WWII then the state of his feet would have had sent smartly out the door of the recruitment office.
Middle Cat has tried. She arranged for "orthotics" to be made - those inserts into shoes which are supposed to help. 
But, you don't wear those in slippers do you? So the Senior Cat has been going through slippers - which he likes to wear inside - at a considerable rate. They simply get worn out of shape so quickly that they won't stay on his rear paws. That's dangerous. 
      "Shoes!" I growl as nicely but firmly as I can.
      "But I like..."
      "No. It's dangerous."
The problem is that he finds putting on his shoes more difficult these days. He hates asking me for help. (I thoroughly understand that as I am equally determined not to ask for help if I can avoid it.)
We did find some "slip on" shoes with velcro straps that didn't seem to be too bad but they proved  not to have the necessary support = and yes, he still wanted to wear his slippers inside.
      "I don't mind sweeping up the sawdust you bring in," I tell him - or the dirt from the garden. 
      "I don't want to make extra work for you," he tells me as he changes into his slippers at the back door.
His father was no better. I remember the absolutely disgraceful pair of brown leather slippers he had. They had been mended countless times - so many times I am not sure how much of the original was left. 
I have suggested "ugg" boots - at least they might not fall off.  No!
Middle Cat bought some plain looking slippers intended for the females of the human race. They had velcro fastening.
   "You can do those up nice and tight," she told him. He dutifully wore them. 
They lasted no time at  all. There was no support in them and those flat feet had them out of shape in no time.
     "I need a new pair of slippers," he told me yesterday, "I don't know what I do with them."
I am wondering if I can find a pair of canvas house shoes such as our Chinese neighbours wear. They won't give him any support but they would probably stay on as they have elastic right around the uppers.
Or maybe I can simply knit and felt a pair to fit his flat rear paws?