None of the hoses are available in the UK any more. Used or a German contact to buy from Tradition (which we have) are the only options.
Are you sure its a rubber hose though? That pic looks to me like its the metal pipe joining the two heads together. That is sealed to the head with an o-ring which frequently perishes and disintegrates.
If it is the o-ring thats a mixed blassing - it's still available, but its a hell of a job to change it, plus you'll need a bunch of other gaskets and seals for everything else that has to come off (inlet manifold etc).
