I'm using a Thule (Yakima does not have a fit kit as of a month ago for the 2004 Prius) roof rack, which you can get the details using Thule's online rack configuration tool. CarRacksDirect has them at good prices shipped free. Do a search for rack, Thule, and Yakima in the PriusChat forums for more info. Rear hitch rack is also an option using the Coastaletech rear hitch upgrade.