1) my baby drinks breast milk, not formula, so what i do is bring an icepack along with the bottle of breastmilk to keep it cool, then when it's time to feed baby, i get a bowl from a restaurant and ask for hot water to heat the bottle of milk. so even if you do not plan to feed your baby with formula, you still don't need to buy a 奶樽保暖袋.
2) there is no bacteria in a steamed bottle, so even if you place it in room temperature, it won't breed germs--unless you put it somewhere dirty or you touch the inside of the bottle or the nipple when you take it out from the steamer. as long as you keep the inside of the bottle clean, you can just leave it in a clean storage box in room temperature. no need to keep it in the fridge. i never put mine in the fridge and my baby is super healthy, never got sick, and she's 5 months old la.