|my portable charger|
That's why a portable charger, like this one (which my husband once gave me,) can be a lifesaver. I keep one fully charged with me when traveling or going to work, so that I can charge my phone wherever and whenever. I've even stuck the charging phone into a pocket, wires and all.
Last night I lent it to the people driving us from a wedding to Ariel, since they were following directions on Waze, and their phone was almost empty battery-wise. (They were in a rental and didn't have a phone charger.)
Besides the protective case and screen cover I got my phone immediately after purchase, I consider the charger the most necessary of accessories.