You can keep your baby's' bottle warm on the go by using a compact milk warming wrap.
Simply plug it into a USB power bank or power source. The warmer wraps around the outside of the bottle and use the control switch to turn it on. Select your desired temperature and timer from the three options available.
30cm x 14cm size (suit most bottles)
Velvet outer layer (see image)
Low voltage (5V)
*designed to keep bottles warm, does not heat cold milk effectively. Some bottle types work better than others.