you really should try to determine "what" type of Plastic it is that you want to repair. I would use "Loctite" they make many different adhesives for what you are looking for.
Some epoxies will "NOT" work on plastic. The west system that S7horton mentioned, I have not used but know of others that have and they claim great results. And yes, it is expensive.
Some epoxies will "NOT" work on plastic. The west system that S7horton mentioned, I have not used but know of others that have and they claim great results. And yes, it is expensive.