Most carriers, as you are probably finding out stop writing at 64 and a half. There is a temporary plan called "The Bridge Plan" which is designed for people waiting for Medicare eligibility. It was originally designed for senior age people who move into the USA
from another country at which time, they will become eligible to participate in Medicare after a minimum of 5 year permanent residency. This plan later found a niche for US citizens who are either waiting for Medicare or missed their enrollment time and now have to wait to apply for Medicare later (first quarter of the following year, with benefits beginning July 1st afterthat!).
You can find the Bridge Plan through many brokerage outlets. If you have a problem, I can forward you the information.