Canon DB9, Atari pinout with 2 separate fire signals
This is the pinout scheme for a SEGA SC-3000 joystick soket.
You can use almost every other joystick which present this plug. All SEGA Joysticks and Gamepads have ATARI 9 pin plug and are compatible with SC-3000. Other ones, in most cases, even if they present 2 fire buttons, they have just one fire signal on pin 6 ( LEFT Trigger ) connected to both buttons.