Have to buy the whole assembly, wastegate actuator. Most vendors sell these, PT&E has them for $79 and they have the HD 18# ones if you run 24# all the time with alky or something, this is probably what you would want...just be careful if you don't have race gas or alky otherwise sometime.
Also, be sure your "Y" orifice is setup correctly in the vac tube from solenoid to turbo and actuator....straight side goes to turbo compressor housing. I've switched these on mine and had no effect, but others have found an effect...it keeps the full boost pressure from being at the solenoid, but functionally should do the same job, just don't know if full boost all the time will hurt the solenoid.