OP; Some thoughts to aid your effort;
1) Freewheel axles will always be more prone to bending / breaking than a cassette based freehub. Just a matter of how much of the axle is unsupported. Primary reason that freewheels went away long ago. Good riddens, in my opinion.
2) If you find a machinist who will make an axle for $10, then have him make 1,000 and get rich reselling them. Well you might find a retired guy with a mill in his garage. Frankly, otherwise the SS blank he would need to start is going to set you back about $20 to $40, plus shipping. Then even basic shop time is going to run $50 to $150. Basically just have the wheel rebuilt with any modern cassette freehub and the problem goes away. If you need the wheel to look old and antique, then it is pretty easy to age the finish on the new hub. Google or you tube will have lots of instructions on that.

Hope that helps
/K