Hi meadowlark and thanks for contributing your question to Car Rack Resources.
It does appear that the major car rack manufacturers (Yakima racks and Thule racks) do not have a trunk bike rack that is compatible with the 2007 Subaru Outback wagon. It may be that they are still working on a solution to this or that the design of the Outback just won't match any of their trunk racks.
However, the Saris Bones bike rack does look like it's compatible with your car. I happen to think the Saris Bones (comes in two versions - Bones 3 for 3 bikes and Bones 2 for 2 bikes) is the coolest looking trunk bike rack available anyway. They claim some famous italian designer came up with the look and I believe it because the curves are just ridiculously hip! The bikes load up and travel really easily and snugly too.
One fine point to remember is that you will also need to buy the Saris Hatch Hugger straps too. These work in combination with the Saris Bones bike rack so it fits correctly on your 2007 Subaru Outback wagon.
Check out both the
Saris Bones 3 trunk rack and the
Saris Bones 2 trunk bike rack for more details.