It happens all the time. You need a USB cable to charge or sync your iPhone but you can't find one. Caseinity
has come up with a novel approach, by including a short cable clipped to the interior of their case.
The case comes in white or black, although the short USB cable is white in either case. There is some added thickness, as you might imagine but it's not excessive and it incorporates a honeycomb protection layer, so you're getting a decent case with a nice extra.
And at under $30, the Cord-on-Board case
comes at a decent price. And you'll have peace of mind, knowing you can charge and sync as needed without hunting for a cable!