replacing the heater hoses on the blue 2.5L 156 2001

[cc]

Hi
The heater hoses are starting to fail and havent been able to source oem replacements.
Have discussed this with a retired boilermaker and floated the idea with him of replacing the hoses with some custom bent metal piping in a suitable metal. With  short straight hoses at either end to couple the metal pipe to the engine and the heater.
Issues i can think of include the need to put in some support metalwork to hold the heavier pipe and possible
galvanic corrosion if the wrong metal is used. I dont think aluminium responds to pipe bending without fatigueing.
Maybe thin wall steel?