Recycle a used light bulb. Put on a pair of safety glasses. Get a pair of pliers and pull out the top of the bulb. Take a Chinese chop stick and break out the inside parts. Rinse out with water before adding any plants.
Reply to Jared:
The base is a separate piece of glass - the ones I used are sold in craft shops...secure with E6000 glue or any other strong bonding glue (in well ventilated area or preferable take the entire project outside to glue - do not inhale any of the vapors.