Answer:
Another possibility is the Tidy Seed large feeder. I have the small one for my parakeets and cockatiels. It's designed so they eliminate wastes outside the feed compartment. (See link below). It's a little pricey, but in the long run it's worth it since it not only prevents the bird from eliminating in their food, but also makes the area around the cage easier to keep tidy since the cracked hulls, etc. stay inside the feeder.
http://www.drsfostersmith.com/product/prod_display.cfm?c=5059+5950+22381&pcatid=22381