Medicare and out-of-country medical care — what coverage exists when traveling internationally?

My husband and I want to spend 6 months in Portugal after we retire at 65. We have Original Medicare with Medigap Plan G. I know Medicare generally doesn't cover care outside the U.S. Does Medigap Plan G have any foreign travel emergency coverage? Should we buy separate international health insurance? How do expats typically handle health coverage abroad before Medicare age?