hi since the space on the bottom can t be used, otherwise a 4 poles mini jack plus socket was perfect, the only thing i can imagine of is mounting on the base of the shaft a 4 brushes (or better carbon pieces as found in electric tools) system that can can rotate around the shaft base, now the cable connectd to this system should be enough "loose" to let the shaft spin but short enough so that will keep the system in place avoiding that the cable can twist around the system itself, go it? Simone .. i know a guy who maybe could laser cut acrylic pieces to create the "system", have a look at drill machines spare parts for carbon+springs brush type, you also need to make four conductive rings on the base of the shaft. ...sounds complicated though