So you would like to build your own GPU cluster with NVIDIA Jetson Nanos? The Jetson Mate Cluster Mini has you covered. It is a case with a cooling fan to keep your cluster cool. It has room for up to 4 x Jetson Nano/NX SoMs. It has a 5-port Gigabit Switch.
You can have a master and 3 worker nodes and can power the worker nodes on/off separately. You will need a 65W 2-port PD charger or a 90W charger for Jetson Nano and Jetson NX systems.