Radiator degas hose

Hi Guy’s

On my father in laws TD5 we have a small kink in the small degas hose that goes from the top of the radiator under the viscous fan cover and back to the expansion header tank. This pipe I believe is the original and is made partly of plastic and rubber.
I want to replace this entire section with a rubber hose but does anyone know what size and length I need to do this.

Thanks