How can I get low cost ivf treatment?

I have medical insurance through united health care. However my insurance covers only diagnosis of infertility and surgery to correct bodily defects, but not in vitro. I'm 41 and running short on time. Please help with info...if you are a doctor and can help let me know...I have 3 much older children and I have unexplained infertility. I can fly anywhere in world, airline employee.