While some free-standing objects look great, they can look cluttered or too big once placed inside of a cloche. Gather several objects, and then try them beneath the cloche top to see how their shapes, sheens and textures read beneath glass. A general rule of thumb: most objects will need roughly two inches of clearance all the way around to avoid looking cramped.
Cloche tops and bottoms are specialty items and aren't routinely found through most major retailers. Excellent sources for cloches are antique stores, wholesale commercial display showrooms and craft stores. After the proper-size cloche is found, it's wise to always buy a second glass top in the event one breaks. Place objects inside of cloche to see what fits properly. Once the best object is decided on, place it in the center of the cloche base.