Verizon Wireless offers the hard-to-find Apple Lightning to USB Cable, model no. MD818ZM/A, for $19.97 with free shipping. That's $3 under what Apple charges directly, plus this is available for immediate shipment (most merchants have a 2 to 3 week wait time). Sales tax is added where applicable. It features a proprietary chip that allows syncing and charging via your computer's USB port or to the Apple USB Power Adapter.

Update: As a reader found, with stock varying by location, The Apple Store has it for $19 with free in-store pickup.