The easiest thing to buy is a length of "all-thread" rod in 3/8" or 1/2" diameter. It's available at any hardware or home store in lengths from 1' to 3' so buy a length you need or cut down one that's longer than necessary. Also buy two nuts and a stack of large diameter (fender) washers for use at each end. I size mine to bear on the outside edges of the cups and use a disk of leather under the washers to protect the cup edges.