Ready to feed formula?’

So my daughter (2 months) is taking the ready to feed Similac formula Neosure. She was bron 4 wks before her due date therefore she was in Nicu for 2 weeks. She never liked the powder formular because all they fed her was liquid or my breast milk. Anyways m, now is a lilt bit of a problem because after the bottle is been open you have 48 hrs to drink it which is fine and you have to refrigerate the milk. My problems is when I go out, I have a bottle that can keep the milk cold or hot for a few hrs, but still not enough and sometimes I’m out for more than just a few hrs and the milk goes bad which of course is definitely not healthy for the bay. Idk what to do. I have throw a few 32oz bottle milk because of it and you know they really pricing!! I was thinking to warm up the milk first and pour it into the bottle that keeps the milk warm which I think is good cause I feel it’ll last longer the milk getting a little bit cold than the milk getting warm and bad. Idk if it makes senses?! 🤷🏻‍♀️🤦🏻‍♀️ but I need any advice. I cant change her type of milk because thats all she is going to drink until she is 6 months(Told by my doctor)

ANY ADVICE!!!