Small steb centers are available from Packard Ind I think they run around $70.00. I would hesitate buying an inexpensive copy. The Robert Sorby piece does the job quite well. Be aware also you need a revolving steb and a drive steb center, both need to be 1/2". I have turned some of the three sided boxes and you can take my word for it you don't want that piece to come loose. It turns at a high speed. I spent a couple days with Cindy in Jan this yr. You can get directions at her web site to make the box. In my mind it is fairly complicated. There are several critical steps in the layout and turning process. However if successful there is nothing else quite like it. I have an order for one now, but feel a little more practice is in order to achieve perfection. I hope this helps,
Jim