Is there a product I can use to fix a chipped crown (like liquid crown)?

Sorry tomassi, I can't think of anything. Often the dentist has to borrow a porcelain repair kit from the lab if it can be repaired easily.
Is the chip on a crown at the front or the back? Is it unsightly or rough? If it's just rough you might be able to take a fine nail file and smooth it as a temporary fix.