I, and many others have used brass lamp finials, available in electrical section of hardware stores. You do have to drill the hole through the top of each one, though, to use as ship mounting.
Lately I have been using clear acrylic (plexiglas) rods, as in this cruiser I recently finished.
For plastic ships I glue in a piece of wood before drilling the holes to reinforce the mounting of the rods. As soon as I do that, I match drill a scrap piece of wood, which is then used as a pattern for drilling the final display base. Actually, I recommend doing this when using finials too, though that is not quite as critical as when using the plastic rod.