Any clear insulators that work well?
Answer:
Difficult.
You lose cold (or heat) by 3 things, convection, radiation, and conduction. Foam traps air in little pockets which limits convection currents. Vacuum bottles have a space with no air at all, so no convection. Foam is opaque, which limits radiation. Vacuum bottles are mirrored to limit radiation. Foam makes the conduction paths long and thin. Vacuum bottles limit the conduction path to where the parts come together.
You could have a vacuum bottle without the silver mirroring, but it would not work nearly as well. You could have other materials that act like foam but they would be bulkier and probably much heavier.
You might be able to work something out with a Plexiglas shell filled with areogel. Areogel is very expensive and very fragile. Check the source link.
Light getting in will heat up your food. That is a no-no. And coolers are usually just bulky because space is a good insulator.
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