Frenchy,

Sorry I don't know who might have them in France. Locally, a lot of sports stores and surplus stores carry them. By far, the most common type here is the "Grabber Mycoal" brand:

http://www.grabberwarmers.com/warmers.htm

perhaps the company could suggest a source close to you, if mail order is inconvenient.

I'm particularly fond of the "Heated Headband" at the bottom of the page. This makes an amazing difference in real cold- probably more than a thick jacket.

Hope this helps...