Product Recommendations Please! Warming bottles on the go..

My family loves to have dinner out frequently over the holidays and I know I will enjoy dinner a lot more if we just give our son a bottle at the table (if it is a feeding time).. I am wondering if anyone can recommend an on-the-go bottle warmer that they have used and liked? I will probably have the bottles in a little cooler, and my baby is only used to taking a bottle that is at least a little warmer then room temp.

I know so could ask most places for a mug of hot water, but if a good product exists I would rather use that.. My sister is in the same boat with her newborn so it may also be a nice gift idea for her..