If you are handy, the construction instructions for knee wall cabinets should work.
I thought of that too. There are various providers that can be found in search engines under "custom mirror cabinet with sloping roof." Qualitatively, I have no idea what they do.
I would probably take a hybrid approach and build a suitable shelf, in front of which either a door with concealed hinges from the kitchen sector (or a sliding mechanism or a piano hinge for very thin doors) is installed. I would then glue a mirror onto the door. Interior lighting with LED strips, exterior lighting separately.
As an argument against a mirror cabinet and for alternative shelves as suggested by , I would mention the organization of utensils in the theater area. No one there has a mirror cabinet because when you take something out, the mirror is gone. Professionals find that impractical, so they make sure the utensils are easily accessible without the mirror disappearing immediately. And doesn’t your wife deserve the most ergonomic and professional solution?
I never understood why women hang a handbag as a handicap in the crook of their arm.
I also never understood why so many women bring a man as a handicap into their lives. They are just strange. I, for one, prefer a woman as a life partner...