what numbers are on your current bulb.
just call one of the suggested vendors and they should be able to quote you a price.
Or go to beseler's website and check for parts or call them.
light source type is important, it is going to be either a cold light, dichro head or a condensor, The condensor type heads have several different types of sockets; screw or bayonet. color heads use a different type bulb and have a plug in connection. A cold light head is a special coil.