Looking for a good hiking map of Île-de-France

In addition to the helpful information provided on this forum, I have also used with success tourist bureaus in both France and Spain. So...

I do not know of anything better than the map you have found, but if no forum member is able to come forward with a confident response to your question, I would check out the link below and query* the FFRP or the Comité départemental de la randonnée pédestre in the department(s) in which you want to hike. The link also includes a link to the French IGN maps which may possibly provide the exact answer to your question.

https://www.angloinfo.com/how-to/paris/lifestyle/sports-leisure/walking-hiking

Another possible source to query is this French hiking forum:
http://www.aucoeurduchemin.org/spip.php?page=forumgeneral

Hope this may help. Bon chemin.

Tom

*query means translating your inquiry into French or start in French, excusing yourself, using some form of online translator, and then switch to English.

Your best bet is to get a blue French IGN map when you get to Paris, for the area as far as Epernon. (ETA These are very large scale maps and you may need more than one, but they are totally worth it.)
Once you get to Epernon, there are custom maps and superb directions available from the Eure-et-Loir pilgrims' association:

http://www.compostelle28.org