After we sold our house (which we had insured with Fireman's Fund) we obtained a renter's policy from them and a $1,000,000 "excess liability" policy that amazingly covered our Rawson 30 OR any boat that we owned up to 45 ft, anywhere in the world. Amazing really. I still have a hard time believing it. The renter's policy was about $500/year for $250K of covered goods and $100K of liability. The "excess liability" (sometimes called an umbrella policy) was about $400/year as well. Boat insurance for a small, cheap boat like the Rawson would have likely been cheaper but we needed the umbrella policy for other reasons. We still bought BoatUS insurance because it was cheap on the Rawson and easier to get a marina to understand that yes, we're insured, than the Fireman's Fund policy. We now keep BoatUS stateside for our boat and have USAA for a "worldwide" renters' policy and umbrella liability policy.
Most of these umbrella policies have limits on boat size from 30 ft, 35 ft, 45 ft, etc. Our boat is larger than the limits unfortunately so it's a moot point for us.
If you're eligible to use USAA, you might consider it for the renter's insurance--your household goods/clothes/everything are covered even if on your boat--no the boat is not covered but all the stuff you own that isn't part of the boat is covered worldwide. USAA boat policies used to cover worldwide but now are limited to US, btw.
PANTAENIUS and Jackline are names that come up in conversation regarding insurance outside of the USA.
I know Ken (Trim50) was trying to get BoatUS insurance extended on the West Coast down to PV Mexico. You might give Boat US insurance a call to see what they can do if anything for you. Probably not, but hey, they may have an associate company
Lloyds does a great job with hull insurance but I don't know about just liability.
Here are topics on bluewater insurance on the forum: