Definitely available at a large hardware store (Lowes, Home Depot, OSH)

MPT... male pipe thread

Edit: I just remembered that I have my old radiator with this repair in the garage. If you want I can send the fitting and the washer/"O" ring set up I used with it. Email me if you want it. Bruce

__________________
The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)