You can get your US tanks filled in many places of the world, but sometimes its at a premium and sometimes its not possible. Bring a hose with a fitting for your propane
tanks on one end and leave the other end open for the various local fittings which you can buy and install. We have used fittings for French, Turkish, Italian, and Campinggaz tanks.
Then beg/borrow a full local tank and fill your tank by connecting the two tanks with the hose. Generally, you hang the full tank upside down and leave it in the sun while you cool the tank to be filled with wet towels. Note that filling tanks like this is probably illegal in a lot of the developed world, so you need to be discrete. It also gets a bit tricky if you are going between propane and butane--don't do it unless your tank is fully empty. If you aren't sure how to use the hose, get another yachtie to demonstrate the first time. Sometimes you can give your tanks and your hose to the local propane guy and he will do it.