Yeah, I just bought an extra lightning cable then went to Microcenter for a dual port USB car adapter. Plug in = instant car charger. At $19 for the cable and $3.75 for the USB plug, it's quite a bit cheaper than I'm sure the dedicated car chargers will be.
You should be able to get spare lightning cables at pretty much any Apple store. I bought 4 extras (one for my nightstand, one for my home computer, one for my work computer and one for the car). The one that came with it is plugged in down stairs so I can charge there during the day if needed.