That term 'boost jet' is kinda misleading since it leads most people to believe it's some sort of high tech device. But it's not.. its just this brass (?) plug with a hole through the middle.. about the size of an eraser on a pencil.
You can use welding tips, available at most hardware stores (Home Depot) and achieve the same thing as the boost jets that JWT normally supplies. Just be sure to get them in 0.045" size. You may need to cut them in half since they're about an inch long.