Found these on sale at Amazon. Schlage RS100HC V N N SL Home Door and Window Sensor - with external contact sensor They are $28.90 when you checkout. Good to use as a normal sensor, or according to reviews they contain an undocumented screw block inside for connecting your own wire pair to trip the sensor. I intend to try and marry one of these to a relay and my doorbell system.
All of the Schlage Nexia devices are currently 20-25% off during checkout. This includes the Trane thermostat, the Schlage door locks, the motion sensor, as well as appliance and dimmer modules.