@dspdrew there are so many things to consider here and that's why you arn't getting a response - it's not ideal.
1. You want something that works with your NVR which means you have to have an ONVIF at minimum camera.
2. This is going to require a camera that is hardwired and powered - providing POE to a door peep hole is difficult at best and results in exposed cords or cords in pinch points in the door frame. While there are door hinges that account for power cords you then have to route them though the door.
3. Bottom Line - What ever you do, if you want it in the peep hole of you're door, it's going to look janky with cords, etc.
There are a TON of stand alone video peep holes that are battery powered and have a monitor inside for viewing that have an SD card etc, those are prob must simpler for what you are trying to accomplish they just won't feed the NVR. I would sooner deploy one of those if you "must have a peep hole monitor" and then deploy a standard IP camera that feeds your NVR beside the front door for better coverage and higher MP anyways.