Ebay is your friend. International should be no where near that price. The international cord is not as nice as the Ford cord. The Ford one is a VERY nice piece, with that said, I got the one on ebay myself.
Do yourself a favor before spending the money, crawl under the truck and MAKE SURE you don't have one, sometimes they come with them, but they're tied off way back behind the bumper out of site. Look at the block heater and make sure nothing is plugged into it. (probably not one there, but it's nice to check), then order one.
Here you go, $20 buy it now. This is even nicer than the one I bought, mine didn't have the 90 deg bend on the end of the cable.
New Ford Powerstroke Diesel Block Heater Cord 6.0 6.4 L: eBay Motors (item 250718388674 end time Nov-04-10 13:49:29 PDT)