NAT and port mappings project

Hello everybody,

I am trying to build a NAT device that will do the job shown in the attached picture.
I have been doing some research but can't find a solid starting point.
Not sure if this is something already available in regular routers or managed switches but I would like to hear from you.

At the end of the day, I want to have some device(Maybe a windows PC, or a raspberry PI or Intel stick or whatever possible...) with a configuration window that I can change my mappings and settings on. This device will have on public IP address(Connected to the internet) on one Ethernet adapter, and another Ethernet connection to a switch of local devices(192.168.1.x devices).

The point is that any client PC on the internet connected to the NAT device, can access any of the local devices of the NAT on the network (192.168.1.x) by connecting to a socket on the NAT device with a specific port number.

link for image: https://drive.google.com/open?id=131z8qYVtT1vME8h7a_57NBNKSdfUUy6h

Any help or guidance is appreciated.
Thanks.