Cast Iron Guttering as Alternative to Plastic Mini-Flow for a Shed? Drainage and wastage systems and plumbing help, advice and answers

[Lkwit]

Does anyone know where I can source cast iron guttering for a shed. I'm looking for guttering which is about 2 - 3 inches high and the same again for the width. I'm looking for a better alternative to the current plastic mini-flow options.
Many thanks