You can use a normal french intellivision cable and don't need rf or else and check the normal UHF VHF CANAL 36, Trust me, i'm french....and congrats for your fiend on Le Bon Coin, i've seen that one but i already have one boxed !
This one is the Telegames one, and it was sold in some Europeans country in the 90's, and some guys imported in France in few copies via their webshop in the late 90's (where i found mine in 2001 or 2002)