MZ/MuZ Riders

While replacing the front tire of my Traveller I noticed the speedo unit mounted to the wheel has several cracks causing the grease to fling out. I'd like to replace it before it completely fails. Does anyone know specifically where I can locate it & the cable to the speedometer. There's probably a Yamaha replacement but have no idea where to start. Any suggestions are greatly appreciated. My Traveller currently has aprox 73k mile and going strong. I ride it weekly.