Swivel screen alternate for D7100?
There are dedicated HDMI secondary screens you can buy (go to BH photo and search for "dslr monitor") and you'll find a a wide range of screens from about $300 all the way to $1000 and higher. Most of the time they're used for liveview video. this allows you to view pictures. If you want to control the operation of the camera, you need to use Camera Control (Nikon) and a laptop, or if you're using an Android tablet with a full USB host mode (like the Samsung Galaxy series and other premium tablets) you have an Android app for what is effectively tethering.
But all of these solutions are much larger than the camera itself.
If you really need a swivel screen that's convenient the D5200 is your only Nikon choice. You'll need to choose another brand if neither that nor tethering is acceptable. Nikon kind of doesn't believe in articulating monitors, in much the same way it doesn't really get interface design for video...especially for its higher end bodies.