1.6Hdi Coolant tank expansion pipe

Hi

My coolant expansion pipe (the very thin rigid plastic pipe with two click lock connectors that go into the radiator and the coolant expansion tank) is leaking at the radiator end. Unfortunately it is not the O ring as the coolant is squirting out where the pipe meets the connector.
I have looked for a replacement pipe but I am not having any luck.
Is the bore of the pipe vital or can I replace the pipe with a larger rubber coolant hose and fix it with jubilee clips?
If I do need the correct hose can you suggest where to obtain one from?

Thank you
Simon