There is a campground that I have stayed at right outside of Blois. Blois is a beautiful city on the river. If you are lucky, the chocolate factory will be working and the air will smell of chocolate. At least there used to be a Pulain chocolate factory there; I assume it's still operational.
So check out the campgrounds in the area. I'm sorry I cannot remember the name of it. It's likely to fill up with the Tour coming through, so check soon.