What to do with broken outdoor lights that left the bulbs exposed?
Exterior light fixtures are designed so that the casing protects the electrical components inside them from the elements. Without an intact case, hail could break the bulb itself in the next storm, or rainwater could get in to short out the electric circuit.

Your options are:


find the manufacturer's name on the light fixture, and look them up to see if you can buy replacement covers either directly from them, or they may list retailers.
buy a new light fixture and replace the broken one. They are often so inexpensive that this might be the cheapest for you.