Might the police hire a locksmith to brake into a residence after the had received a search warrant?
Yes.
Should the police have the authority to require the lock manufacturer to produce a master key to their locks when none exists?
This analogy fails. Is Apple the criminal? Is Apple being accused of terrorism? Why is your locksmith justified in breaking into Apple, even with a search warrant? Apple has done nothing wrong, so why issue a court order against Apple?
No, they would not use a search warrant. They would break down the door if it was locked against them, or they would serve the warrant on the owner, tell him to open the locked door and if he refused, jail him on a contempt of court charge until he complied with the order. But you are referring to people INVOLVED in the crime. Apple is a third party.
If they bring in a third party, which is some times permissible, it will be their normal business to do what is being asked of them, and it does NOT require them to do something extraordinary which in the course of their business they would NOT NORMALLY DO, especially if that compelled act would damage their business while being forced to act for the government's interests.