Depending on the size of the crack you might try just a strong glue for a small crack. If it's large and/or chipped you might fill it with bondo, or quikplastik or something. Maybe reinforce is from behind with bondo/quikplastik behind it and a bit of superglueish stuff inside the crack?
... and another Q? ... damn im the Q? guy
anyway
what's bondo ... the real name, like the "sintra", any of you have a pic of that fantastic product thanks