Bottle Warmer

My first baby did just fine with breastmilk straight out of the fridge so I have no experience with warming bottles. My newest babe is almost 8 weeks and we have discovered that he does not like cold milk. He does okay if it's room temp, freshly pumped milk but anything out of the fridge is a hard no, even if I run it under hot water for a couple minutes. Which bottle warmers work well for breastmilk and are most convenient? Right now we would only need it occasionally but we need to figure out something for when we want to leave baby with grandparents for a few hours and then later on when he goes to daycare.