Thanks for the reply. I actually did search and saw that thread, but none of those were 4K.
I already have cabling ran to the door; it's not hard at all. I even have existing analog BNC cabling ran there as well for my current analog peephole camera. A typical peephole is a set of lenses that go through the door, so there is really no need to run any cabling outside the door, unless you don't have an existing peephole and don't want to drill a hole in your door, or you're looking for a door bell camera (which I already said I am not looking for).
I will probably just take apart my existing peephole camera and modify a 4K IP camera using the peephole camera's lenses. Hopefully I can get them to focus correctly. It's just going to be a much larger unit mounted on the inside of the door than I currently have, but that doesn't matter to me. If anyone is interested, I'll post the results here. Building my own stuff is nothing new for me.