As sracer said, there are little adapters with two female Lightning jacks to allow the Gen1 Pencil to be charged from a Lightning cable.
I've also seen a "charging stand" offered that was a short aluminum cylinder with a female Lightning jack and a recess to hold the cap. The pencil would stand vertically when charging and you had a place to put the cap so you'd be less likely to loose it during the charge. I don't know if this had it's own USB cable or whether it relied on being connected to a Lightning cable.