Most camera's sold get listed by their manufacturer's name not the shop who sold them. Then there's an ebay problem where searches don't map across from different countries properly so using the US or UK sites doesn't pull up items listed/sold in France, However there are references to Nadar selling British cameras around the 1880's and his visiting London to buy cameras is mentioned elsewhere.

Then it's no coincidence that the Paul Nadar's Detective camera has a similar Nadar name plate to your camera.

Nadar had met with George Eastman, they photographed each other, his son's camera is using Kodak roll film very early compared to competitors.

Searching in English is likely to throw up much information as Nadar was French few of the cameras he sold would have left the country. I'm sure if you looked in the French equivalent of the British Journal of Photography you'd find adverts for Nadar & his camera sales.

Ian