Whatever happened to Zink?

I remember this one book that I read in the third grade. It wasn't required reading, just one of my "reading for fun" things. The book was called Zink, and it was about this girl named Becky (I think. It's been a long time). She was diagnosed with leukemia, and to help her get through the tough time, she 'imagined' up these zebras. They told her about this zebra who didn't fit in because she had spots instead of stripes (this is meant to represent Becky). I really enjoyed the book, and at one point considered stealing it from the classroom on the last day of school, making sure that I wouldn't get caught (but my conscience stopped me).
Ever since then, I've been looking for the book everywhere. In libraries, bookstores, and even online reading sites. Unfortunately, I've found nothing. It's like the book never existed. I honestly wish I knew what happened to Zink.