1995 Mazda Protege Turbine Speed Sensor

I need help I have a 1995Madza Protege 1.5 engine that has a turbine speed sensor problem and it runs but I can't find the parts I need to fit it. I can drive it and sometimes it kicks into overdrive and the engine light is always on. Could you tell me where I could get the part to fix it. It's a good little car put this problem need to be fix now. I had it check and the code p0715 came up. Help please thank u. Pam