Well I'm afraid I can't offer any opinions on Northern French Christmas Markets .......... but there is often one in the Gare de l'Est in Paris ........... seeing that the Maison d'Alsace is not far away!!
Traditionally Christmas Markets started in Germany, and as Alsace was annexed to Germany twice this century and has been in close contact culturally for hundreds of years, it is not unusual to find that the Christmas Market has spread over here at a phenomenal rate over the past 20 years.
Many villlages here in Alsace have Christmas Markets during weekends in December, but there are many outstanding markets open from the end of November, and in the case of my 'home' market - Colmar - it stays open until 31 December - just as colourful and attractive but with fewer visitors! I would strongly recommend mid-week visits if you can!
If you are able to fly into STRASBOURG, KARLSRUHE-BADEN or BASEL-MULHOUSE airports, you will be able to enjoy GOOD Christmas markets in Strasbourg (F), Baden Baden (with hot thermal baths!!) (D), Freiburg (D), Colmar (F), Mulhouse (F) and Basel (CH) (though you'll need Swiss Francs for the latter and it may seem more expensive).
(F = France, D = Germany, CH = Switzerland)
It's easy to get to these markets, but the problem could well be finding accommodation locally, so start planning NOW!! You might find hiring a car is a good way to visit the area and get from the airport but once in the vicinity of the market, I would suggest leaving the car safely in the hotel's car park and taking public transport to the actual market itself.
Should you be intending to visit Colmar's Christmas Market, or Strasbourg's or Mulhouse's, and you'd like more detailed advice and help with booking accommodation, please don't hesitate to pm me.