I need a source for a light bulb to replace the original in a Gio Ponti designed lamp made by Arredoluce [1950's Italian] and called "Cobra Lamp".

The same bulb was also used in a cube shape lamp, name unknown, designed by Ponti for Arredoluce.

It takes a spotlight shape bulb with a 5/8" dia base with 2 lugs [wattage unknown] 110 volt sold in USA.

Many thanks for any assistance.