FWIW, I used a thermos bottle back when I was first diagnosed more than 40 years ago. It was a pain because the ice would melt and make the bottles wet, labels would come off, etc. This was before the days of plastic ice (and plastic labels on the bottles), so you’ve found a fix for that problem, but you’ll have to figure out how to re-freeze those ice-cubes during your travels, which may not be easy.
Anyway, I later realized that it really isn’t necessary to refrigerate insulin, and since then I’ve never bothered and never had a problem. I spent a couple weeks in Costa Rica and Nicaragua a few summers ago with my son, in non-air-conditioned hotels, and my insulin was just as good at the end as it was at the start. I kept my spare back-up bottles in the hotel, and carried my open bottles with me at all times, out walking around in the sun (with some volcano climbing thrown in there).