Sent you a PM, For. It's the one you think it is. Heatsink itself fits fine. The casing around it is the too large portion
Ok then. It could just be that the module was manufactured to the wrong tolerance (it is exactly 1in diameter rather than 0.99 of an in) You may be able to sand the housing down a little if you have a Dremel, belt or drum sander but if not maybe there is a friendy auto shop that might be able to sand/shave it down for you.
Be aware this might be a bit tougher if it is a housing with the lip around it.