I agree with both of them, your average DIY store will not carry stuff like that in the bigger sizes, you may need to go to a plumbing supply house for it. And putting a female adapter on the copper is definately the way to go, and if you don't want to sweat, there are compression fittings that will work also. They have a rubber gasket with a steel ring inside of it that bites the copper, you could get a compression to male pipe thread, I doubt they sell them to female, but you would use a simple iron pipe coupling after that. I am sure that the compression fitting cost at least four times what the regular one does, but just to throw it out there.