Hartal Door Lock

[Lazyboy]

Does anyone know the best place ( do I mean cheapest) to buy a door handle and mechanism for the habitation door on my Carthago. It is the type that has the counterweights fitted that has been the discussion in previous threads. If memory serves me correct, someone had a new shaft made that the weights connected to. Can anyone recall? I have spoken to my dealer who informs me that they are an issue that Carthago know about but neither is interested in the fact that they are not fit for purpose.
Picture shows mechanism details.
Regards
Lazyboy