The term, should you wish to google first is "finial." These can be found among lamp parts.
For attachment, various methods can be used.
I have used stubby Molly bolts, wher you need a hole that admits the entire fastener, then tightening the fastener expands the sides of the bolt which then clamps down on the hulll. This is very suefull if you find you need to mount and unmount the hull. Mollys are also handy if you want to wire lighting into a kit, as you can use one for the positive and the other for the negative.
Alternately, a bolt like a hex head can be epoxied to the inside of the hull, passing through a drilled hole. If you have not decided ona finial (or a final display height) get longer bolts than you need so you can trim them as needed.
Another way may modelers use is to epoxy a stout piece of hard wood (nothing soft like balsa) inside the hulll. A pilot hole is drilled from the outside of he hull and into the block, with a final diameter hole shallowly boerd only though the hull itself. A wood screw is then passed through the base, the finials, and then into the block within the hull.
The downside to wood screws is that they can't be backed out too often, and you have to be careful not to strip the hole, too (a possibility if you use too large a pilot hole).
The most exotic way to mount a kit is one I've not yet tried. You glue rare-earth magnets inside the hull, and use steel bolts cut flush with the finials to attach the kit. Rare-earth magnets have a powerful pull at close range, and thus have significant gripping power.