Amazon has a Fosmon Extra Long 6 Foot (6ft) Apple iPhone/iPod Charge and Sync Cable for just $1.35 + free shipping. This is twice as long as the standard cord and it gets good reviews compared to others in this price range.
Shipping is free but does come from China, so it will likely take a few weeks to arrive.
Please remember: Amazon prices can change very quickly. Please verify that the price is the same as what I post before purchasing. As of 8/29/13 at 1 PM, this listed price was accurate.
Disclosure: This post may contain affiliate links. When you click on these links, you are supporting this blog. Thanks!