Is it obligatory to impose the hijab on non-Muslim waitresses working in a restaurant primarily frequented by women, and what is the religious ruling if it is not imposed, given the difficulty of finding veiled waitresses?

It is not permissible for a restaurant owner to allow unveiled women, Muslim or non-Muslim, to work for him. Rather, he must oblige them to wear the hijab and prevent them from displaying their adornment. Leaving them as such makes him a partner in sin due to his violation of Allah Almighty's saying: "And cooperate in righteousness and piety, but do not cooperate in sin and aggression" (Quran 5:2), and the Prophet, peace and blessings be upon him, said: "Each of you is a shepherd and each of you is responsible for his flock."