Thanks kakeladi for explaining why I couldn't comment on my own post. 

Yes, I'm referring to separator plates with columns.

Bottom layer large square, next layer small square (offset to the corner, not centered), columns, then round on top

So all you need is one plate 2” larger than that smallest cake & 3 or 4 pillars .  You say your having problems finding that?   Where have you looked?  Wilton site?  eBay; stores like Michael’s  Joann fabric, hobby lobby have them    

There are “push in pillars” so just one plate is needed.    Or you can use 2 plates w/pillars between.  I see no need for a sq & round  & no! they will never line up for use together