A button box with 10 Buttons and two push button rotary encoders as buttons 11-16 using an Arduino Leonardo or Pro Micro to host a controller for the button box. You will also need to add the Joystick library from Matthew Heironimus (https://github.com/MHeironimus/ArduinoJoystickLibrary) as well as the "RotaryEncoder" library by Matthias Hertel to compile and write it to the ProMicro or Leonardo board.
In addition to this you would need: Arduino Leonardo or Pro Micro 5v 16mhz a small breadboard to place it on if you don't want to solder the cables onto the board directly a enclosure to host the buttons 10 buttons of your choice. I just used momentary switches 4 round (https://www.jaycar.com.au/small-black-spst-n-o-momentary-action/p/SP0700) and 6 square (https://www.jaycar.com.au/pushbutton-push-on-momentary-spst-red-actuator/p/SP0716) 2 push button rotary switches https://www.jaycar.com.au/rotary-encoder-with-pushbutton/p/SR1230
See attached wiring diagram.