As mentioned a one-piece is likely a pretty penny. The one linked above is tree-fiddy plus tree dollah shipping.
Though that Belkin dual wall charger is a pretty nice package for $20. There is a comment on there (Amazon) about the cord not working for sync though.
I just ran into this problem myself...mostly because I use an older iPod touch as an alarm clock/weather checker/email client and needed to extend both my iPod and iPhone power supplies. I found the solution to all my problems at monoprice...
For around $13 (shipped) I purchased 4 USB extension cables...so there you go...problem solved.
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I have one from monoprice and like it a lot, works great and is good quality.
I've heard these cheap ones don't always work for long. However, I've considered buying a number of them anyway, since they're so cheap. Obviously, they shouldn't cost what Apple charges.
I strongly encourage you to join 20 to 30 small USB extensions, all put together, and connect the iPhone to it. I use it to make a 20ft cord and it works like a charm. It even gets wet and it still works!