"It sounds like you haven't done a thorough evaluation of the available technology to provide you with a proper part to acceptable tolerance using an efficient and relatively affordable workflow."

Again, not true. A machine shop tells me they cannot machine without a nurbs based file. Another machine shop tells me they can machine from an STL, but the size I need is too large for their equipment. I did not fabricate this information, it is true.

If you can draw an intelligent conclusion from this info, then you are smarter than I am. That is why I say I need more information.

At this point it makes sense to deal with the service that can handle the size, and give them the file format they require to do the work.