FWIW, the inside diameter of Gitane TdF steerer tubes WILL accept a conventional 22.2 mm quill stem - thanks Chas.! - but you may have to work some on the headset locknut. On my bike, a previous owner replaced the Stronglight headset locknut with a Zeus unit, which nicely accommodates the Nitto Technomic Deluxe I am currently using.
Add me to the chorus wanting pix!