There are companies that specialize in insuring offshore
boats; these companies & policies are different from the local/coastal policies that you may have already contacted.
Yes, you can get a policy with "Worldwide" navigation
, but most
people don't go around around the world in the 12-month policy period. So you would start off by asking for a quote through an offshore/world cruising insurance
company for just the navigation that you will need for the first 12 months.
And you can get full hull
coverage, or if you can't afford that, you can get P&I Liability Only coverage.