I don't know the specific route you are planning but, I mapped out the general route on Google Maps, and there do not seem to be any significant 'dead zones' where you are truly out of civilization for any distance. When you are closer to the day you want to ride, select a route that hits a small town or village in the middle of any stretches that you fear you may need to resupply.
Also, I have found myself out of civilization in the past and in need of water, and I have never been refused when going up to someone (house, business, church, etc) and asking to fill my bottles.... you will likely see someone watering their lawn and you can just ask to borrow the hose.