I went to Best Buy at opening and hunted all around in the their abbreviated video section to no avail. There was one of those rolling carts of stuff to be put on shelves, but I couldn't spot it in there either. After finally flagging down a blue-shirt and giving her the details, I waited as she keyed all the crap into her computer.
Then she looked around again and called on her little communications device to locate the person in charge of the department and went to speak to him. Finally she came back and told me that these "Sunday flyer" discs were all up front in a display - the way they used to be in the glory days of Best Buy.
So I grabbed a Season Five set and went on my way. I decided not to get the Unification disc since both parts are included, and the price was a little higher than for Season Four.
Happily, Unification I and II are on the same disc and not split the way most two-parters were in the DVD sets.