Have you quoted a regular insurance plan's prem when you are just 60 years old?
I have a friend who retired at 56 from California Education System. She is dual nationality - Canadian and American.
CalPer has excellent medical coverage - that would covers her as she was still working, until 61. After 61 she will be on her own. She checked around - the regular insurance for the similar coverage she had, would be $800 a month.
She was thinking about 2 options - move back to Canada until she turns 65. She prefer living in US than in Canada.
The other option is to move aboard - Portugal is one country under consideration because medical insurance is less than $200 a month, worldwide coverage EXCEPT US. Or moving to Mexico where medical insurance is cheap and medical care standard in certain places are high.
So I dont really understand what your desire is? 
You can find a company that offers plan that covers you everywhere and also would cover you after 65 as long as you still work for them. Or, find a substitute to replace Medicare which you feel is inferior, if you dont mind to pay $800 to $1000 a year. Just keep in mind when you change your mind (no punt intended) and want to sign up Part B but passed the initial eligibility period, you would pay a penalty and a much higher premium. 
