Thanks for letting us know about this. If you decide it's not worth it to supply parts maybe pass some contacts along to someone else who can take on supplying the stuff that is needed? My dealings with China have been positive. Having said that I only purchase small items never anything as expensive as a milling machine. For things like ballscrews they are generic and it might be worth it for someone to make them as required.
Hope things work out for you in the long run.