... I'm not sure a cable like that will fit on the machine because of the handscrews on the sides of the plug, that is, this plug is wider....
everything fits with the help of a dremel

seriously now, is it maybe an option to take a old joystick at a fleamarket and just mount that cable in the keyboard ?
I understand that a extention cord is way more nice , but if they are so rare to find....
or cut a cable of that joystick / gamepad and find a female plug, that is not the connector that has to enter in the unit so that might also work out...