Tousley has a great price on the flash kit for $220. I know some people were able to wrangle these from their dealers for free, but if you're paying, this is one of the better prices I've seen.
http://www.tousleyfordparts.com/partlocator/index.cfm?action=MorePartInfo&PartID=1105627&siteid=214771&catalogid=5684
http://www.tousleyfordparts.com/partlocator/index.cfm?action=MorePartInfo&PartID=1105627&siteid=214771&catalogid=5684