Compact mill storage solution

Milk**

How do you manage to store your milk when going out for a day?

When I need to bring milk for a day out I usually thaw it and then put it in a thermos that will keep it cool without a cooler and bring my portable bottle warmer along with his bottles. This can take up significant room in our diaper bag.

If I’m out for a long time, I pack a separate bag with my pump and accessories. My problem is chilling fresh breast milk and storing it. I prefer to not put it in regular bottles because they aren’t insulated and they take up so much room. Ideally I would put it in a thermos but I was dumb and realized the thermos would only keep it warm. Could I get those reusable ice cubes and put them in a thermos to keep it cold and then add the milk?