Just buy a tap and handle to turn it with. 1/2 X 20 is common hardware. 1/2 x 24 is fairly common. 1/2 X 28 is just fine thread. Go easy and lot’s of tap magic cutting fluid.
I’ve been through all this. You first have to cut down the outer diameter of the barrel to a size correct for the thread diameter you are going to cut. Second, you have to make sure the die (I have all that) is started properly which will require a threat starting insert in the barrel to keep the bore aligned with the die.
It’s just not as cut and dried as buying a die and handle.