Purchase a polyester paint color that matches the color of the alabaster.
Put enough epoxy glue in a small mixing container to spread on the broken piece of alabaster.
Pour a few drops of polyester color in the container. Use the wooden stick to stir the epoxy and colorant. Keep adding color until it matches the alabaster.
Place the broken piece in the correct position on the fixture being repaired. This is to see if it fits properly.
Dip a paintbrush in the epoxy mixture and spread paint on the back of the broken piece of alabaster.
Place masking tape on top of the broken piece and fixture to hold the pieces together while the glue dries. Fill any holes or chips with the epoxy mixture.
Pour a Little methylated spirits on a cloth and wipe away excess glue. Allow the alabaster to dry.
Sand away any imperfections.