You could make your own with some raw lumber or talk to a local carpenter about making them and letting you install them if you want to do that part yourself.

You can purchase unpainted wood furniture or shelving units that can be inserted into this area. Lots of folks do this on cape cod type homes where the ceilings tend to be at an angle in the room.

Check out what Kyle did: http://www.hometalk.com/member/ff8kfjl29g/ph...

One thing that you are going to have to consider is that in the winter you cloths will get really cold on the outside wall. This may cause some mold problems. If you could put it on an inside wall it would be better.