That exhaust pipe and bellows is metal because it is before the water
injection point. The exhaust gasses can be 800 deg F or so and only metal will handle that temperature.
An exhaust bellows is a manufactured part and it can't be fabricated locally. Buy a new one and replace it.
And when you do, please insulate the pipe. That hot pipe is radiating a huge amount of heat into your engine room. And any oil
leak that hits it will result in an immediate fire!