Hi Stenton:
Wow, what you have described certainly sounds strange. I have no doubt that you have thoroughly explored the insurance options available to you in Malta and the result is the problem you have described.
I wonder if you might be able to get liability insurance cover for off-island activities by going down the same path that those of us who live outside Europe do (for example, what I do to insure my Canadian-plated moto when it is in Europe) - in other words, buy a policy that is intended for visitors to Europe.
There is a huge and long-running discussion about this process here on the HUBB - you can find that discussion here:
Here is where you get the cheap European green card insurance. There is a similar discussion about how to obtain coverage for visitors to the Balkan countries here:
Balkans Insurance - Here's the story, with details & sample documents.
When you click through to go read those discussions, don't start reading from the beginning of the discussions, or you won't finish reading until 2024. Pay attention to the dates of the posts, and scroll down and start reading at posts beginning in 2020 and later.
The suggestion to buy "visitor to the EU" insurance for a bike plated in the EU sounds kind of strange, and I don't know if you would even be eligible to buy this coverage, but it's worth looking into, especially if you only plan one or two off-island expeditions each year. This kind of coverage is sold in one-month increments (for the classic EU green card coverage), and in shorter increments (week or two-week) for the Balkan country coverage.
Be aware that all the different vendors who sell the classic EU green card insurance are selling exactly the same product - minimum third party liability insurance for the EU - so if you choose to buy this kind of coverage, choose your vendor based on price and purchasing (delivery of documents) convenience. There is quite a wide range of prices charged for the exact same thing, with Bulgaria being about the cheapest country, and Germany being the most expensive. Other countries such as Italy & Croatia are in the middle. The final price you pay is comprised of what the vendor pays their local insurance agency for the policy, plus whatever markup the vendor adds to cover their labour, postage, etc.
Good luck, and let us know how this plays out for you in the future.
Michael