You need a kick back hub shell with 3 bands that's either yellow or blue. The red band is a different animal, that hub shell or sprocket wont interchange with the yellow or blue. The hub shells and sprockets show up every now and then here and on ebay. But like ricobike said, it might be easier to get a yellow built wheel and sell yours. Or you could swap the sprocket and driver.
Heres a funny fact, there really isn't a lot of difference in gearing between the yellow and blue. Its like 1 tooth. Yes it is an overdrive but it has a 20 tooth sprocket and the yellow has an 18. If you could get a 17 for the yellow it'd be the same thing.
Something else about the kickbacks, they growl! The yellow and red growl in low and the blue in high. Much as I like these hubs I don't want to listen to the growl. Myself I'd rather have a yellow and tool around in high gear having low gear for when I need it on a hill.