With luck, you may find the fixture, or one like it, at an antiques dealer, junk dealer, or a store that specializes in Victoriana. Then he thought of a bowling ball. You could do the same, although you should consider putting an oak capital on top of the newel as a base for the bowling ball. Be sure to remove or disarm the wiring. When I installed outdoor lights, the outlet boxes were set in openings in a brick wall.
Trouble is, the boxes are loose, so the fixtures are loose.
H.G., Framingham A. Shims should tighten up the boxes. Drive wood shingles or any other flat, tapered wood between box and brick. Make it good and tight, and cut off any shims that stick out with a utility knife. You can buy plastic shims which may work better because they will not expand and contract as wood will. Another way is to mortar the box in place.