I last used a modified mailing envelope that has small bubblewrap. They are available with smaller bubbles in the smaller envelopes. Those thinner bubbles work well enough, long enough, for the foods and temperatures on my hikes.
First, I bought Reflectrix and it worked too well for me. The food stayed too hot for too long, with the first bite burning my mouth when I was very hungry. For winter temps, or for more people than a solo hiker, reflectrix could do well.
Sounds like I'm suggesting thicker cozies for colder temps--what a concept--I could try that on my sleeping gear too. ;)