The #65 yard lights use the same bulbs as the floodlight towers, so Lionel part #600-2313-300 is probably the bulb you would need.
With the plethora of LED bulbs on the market in almost any color, you can easily duplicate the warm white color of the original bulbs, or try something in the cool white/daylight white to simulate mercury vapor or HID bulbs. The ultrawarm whites (around 2200k) would produce a nice orange glow to simulate high pressure sodium bulbs.
-John
