Well Marnie, for a basking bulb, nothing special or expensive is needed. I use 60 watt household flood lamps. (But I also use a full spectrum florescent with it, and those aren't cheap) I get the flood lamps for basking, at dollar tree for a buck. No need to pay $12-$15 for a reptile basking bulb.

The wattage needed depends on your setup. The idea is to have one end of the enclosure be the "sunny" spot, around 85-90 degrees underneath it as long as you can accomplish that while still keeping the cool end in the 70's and keeping your snakes from getting too close to the heat bulb. 60-70 degrees at night is fine. I recommend using a fixture with a dome, and a ceramic socket with your heat bulb but the bulb itself need not be anything special.

This is how I do that: