“Parts can not be fabricated?”
I agree. What is so hard about that. By the way I have 4 varients of the Lee-Enfields.
As others have noted, it's not so much that parts do not exist, but that they are not available from "approved" suppliers, and for the machine shops which could fabricate the parts, the cost of dealing with the government procurement system makes it uneconomical.
They should just sell them to the private market, which could get parts without government overhead.