I've always heard them referred to as a cocking axle. However, Gun Parts Corp., aka Numrich Arms has one in stock, and they call it a hammer pin.
The SKU # is 1576740 and the price is a very reasonable $7.00
Considering that small cost for an original part, it is hardly worth the effort to machine a new one.
I have never seen this part break. The part is directional, and if I remember correctly, the X on one end should be oriented toward the right side. I can double check that before you install it if you want.
