Do you mean something like a wire shelf perch that was bent so it has three sides? There are some examples of wire platform perches here:
http://www.perchfactory.com/bird_cage_p ... erches.htmI also ran across this picture, which isn't quite the same thing but I think it's clever:

You could try looking at accessories for other animals, especially rodents/hamsters/gerbils. There's a lot of stuff for them that's suitable for birds too.