That's actually a common fluid coupling part. Go to any tractor supply store, dealer, or a good hardware store (you know, the one with squeaky wooden floors) and pick up one. If you get desperate, you can use a brass one. Oh ny God, the reaction that statement with generate. It could kill you, the hydraulic oil (they will spell it "hydrolic") will get contaminated, the threads ("treads") with get stripped, the flow rate will droop, and the tractor will look funny with a brass part in it. Yeah, so what?? You're runnin' ain't ya?
Go ahead, order the $200 part from Japan. Our balance of payments is falling behind....
One more thang, If you was really a tractor man, you'd go out and buy that $2500 Miller Syncrowave TIG and put it all back together, you know, OE.