Assuming this is intended for use on a pistol that has a link mounted barrel that moves, I do not believe I have ever seen a generic recoil booster. I believe they are specific by the can maker's proprietary booster. If you are looking for a female to make 1/2x28 adapter, what is the intended use?
More information may help find what you are seeking.
To just screw on the barrel and then screw on the can as if it were the barrel with the booster spring and piston inside instead of having the side that attaches to the can having to be the same thread pattern as the can cap. Seems like a pretty easy concept too me .
It sounds to me as if he has a can that doesn't have a Nielsen device and is looking for an adapter from his barrel to his can that has a Nielsen device. I could be totally off here.
What can do you have?
You're not going to find a Nielsen device that's an adapter. They are all designed specifically for the can they work with. Even mfg's design them different among their own series of cans. I think it would be prone to bullet strikes to have an adapter like this anyway.