Hi there, there is some more things to consider: are you looking for a "travel"-insurance where they pay for the treatment until you are fit for transport to your homecountry and then the insurance
of your home-country continues paying for any further treatment and they are out of the contract
? In this case it means you need to keep the original insurance
in your homecountry active or at least make a deal with them so they take you back. With many of the travel-type insurances (like ADAC for example) you've got to prolong the contract
in person which means flying back, you've got to stay on the move and keep proof of that (a winter-haulout for example means you are not on the move), some of the contracts you can only prolong twice or up to 5 times etc.
The other type of insurance is a full medical
insurance with worldwide coverage. Usually your contract prolongs itself if you don't cancel it, usually you have coverage for a limited time in your homecountry, usually it is a bit more expensive than travel-insurance, but with this kind of insurance there is no need for keeping a second insurance in your homecountry active.
For the second type of insurance there exists Allianz worldwide care (via Pantaenius), but also some very interesting Ex-pat insurances. There exists a thread in the Trans-Ocean forum called "krankenversicherung die x-te", in german of course, but it might be interesting for you.