I am looking at wall mounting my Bravia XBR tv (KDL-V40XBR1) on an external wall above my fireplace, and by my estimates I need at least a 12' power cord. I believe the stock power cord is only 3'. Is this cord just your standard PC monitor/tower power cable? Or is it a proprietary cable?
This TV uses a standard 3 prong IEC type power cable (e.g. power cable used for virtually all PCs and computer monitors in the US).
The manual for this TV shows on page 17 that the TV uses a standard power cable. So, you'd just need to pick up a decent gauge power cable with "14AWG/3" or "16AWG/3" printed on the power cable's jacket.
They sell 12' cables for laptop projectors that use that standard 3 prong power cable. Those projectors come with a 6' standard cable, but you can buy a 12' optional cable that sometimes people need when they ceiling mount the projector, or the projector is on a conference room table. Those are about 5 bucks on the internet.