No separate usb socket, it's just a small 12v cigarette charger in the original under the dash socket. Compatible with most USB devices. Amazon sells them, (as well as any electronics store I presume...)
Here is one example, don't know if it's a good one:
USB cigarette charger Also, here is a link to RAM mount:
Ram Mounts I ordered my bits and pieces as separates via the "Products/RAM Components" menu item. These are the product links, however I guess a lighter type "B" components could be used for holding an iPhone... although I don't know.
Base/car adaptor Arm iPhone 4 holder Ball adaptor 
