I got a stainless steel sippy cup thermos that keeps milk pretty cold
They have tiny hydros and stuff like that. I put mine in the freezer before hand so when I need to take it out it stays really cold and then I have a travel bottle heater since my baby prefers it warm! They also have dupes if a hydro or anything is out of budget (:
Unfortunately my daughter didn’t take to cows milk at all she’s nearly 14 months but the stage 3 toddler milk has been a godsend for bedtime/out and in the mornings. You could try something stainless steel they often keep the temperature cool
There are bags that have the cooler system in them. You can use those and put ice packs inside of them. It helps keep the milk, cool