Hi,
I recently encountered the same problem. I am hatching Ameraucanas from four separate breeding pens in a Sportsman 1502. I called all over the place looking for some of those things that come in cardboard boxes as dividers.
You know the type. They fold flat but they open up in an accordian-fashion and create a bunch of little boxes when open. Well, I have yet to find anything so I wound up fashioning one myself using strips of cardboard and duct tape. As Red says, "Finished the job the Handy Man's way!" Worked like a charm too except that I was a bit concerned about a couple of the connections giving way and letting the chicks get mixed up so I pulled those out before they could.
Now I am having a friend of mine from church fabricate me a similiar thing out of metal so I can just place it in the hatching tray and not worry about it.
Hope that helps.
God Bless,