I don't know where to buy the die but, you might be able to save the threads by taking a small file and clean up the threads on the barrel and save them.
A small thin flat file or a triangle file and go very slow.
Will take some time but they should be able to save them.
Good Luck.
you can also get a "thread file" which is sorta like a checkering file. That is, except there are different pitches, on the square, double ended file. Therefore, on one file, you actually have thread pitch spacing for 8 different pitches.
Made specifically for cleaning up banged/damaged threads, without "re-cutting" them.
You can adjust it to clean up threads without removing material from the undamaged portions and it will to a better job than a thread file. When you're done, use a piece of green Scotchbrite pad with a little oil to do a final polish on the threads.
ETA you can spread it to get past the damaged portion then adjust it until you feel contact with the good threads, a little resistance, then adjust it just a little bit open so it moves freely and back it off the barrel to clean the damaged potion. Repeat & tweak as necessary.