SONY Micro Hi-fi compatibility

My Sony hi-fi system has a docking cable which fitted my iPhone 3, allowing me to play my entire digital radio collection with ease. However, I now have an iPhone 4S, which of course doesn't fit into the dock recess. SONY claim not to have made any such devices to fit newer iPhones, so I'm a bit stuck. Can anyone tell me if there is some sort of adaptor which sits in an iP3 dock, and presents a suitable interface for iP4S, or possibly 5S? Thanks in advance for any help.