Where are you located? I rarely see them sold separately from the tractor. And if they are, chances are that pieces are missing. I recommend looking for a junk A that has the cultivators on it. They are usually cheap. I do know a guy in East Texas that would probably have cultivators.
You're a long way from Texas! The Red Power Roundup is in Spencer, Iowa this June. There is always a lot of vendors there and a fair chance that there could be cultivators there.