I purchased two wood wine cubes that were 20"x20"...lucky me as the width of the cart was 40"
I headed to the hardware store again and found a piece of plywood to put on the top of the wine boxes to be used as a counter. The key to save some $$ is to get a piece that is nice on one side and can have knots on the other. We cut it down to a 16"x24" piece of wood...just enough to have a few inches on all sides.