Peace be upon you.
Grand Ayatollah Sayyid Sistani (may Allah protect him):
There are two scenarios:
First: If the man is not married to a Muslim woman:
In this case, it is permissible to marry a Christian woman temporarily, but it is strongly recommended to avoid permanent marriage. If the Christian woman is a virgin, the consent of her father or paternal grandfather is required, unless she is independent in her affairs and has control over her own matters. If she is independent, it is also strongly recommended to obtain the consent of one of them.
Second: If the man is married to a Muslim woman:
In this case, it is not permissible to marry a Christian woman, even temporarily, without the permission of the Muslim wife. Even with her permission, there are issues, and it is strongly recommended to avoid it.
Grand Ayatollah Sayyid Khamenei (may Allah protect him):
It is permissible to marry her temporarily, but it is strongly recommended to avoid permanent marriage. For a virgin Christian woman, permission from her father or paternal grandfather is required, and the contract is not valid without the permission of one of them.
Grand Ayatollah Sheikh Wahid Khorasani (may Allah protect him):
One of the reasons for prohibition is disbelief; thus, it is unanimously agreed that a Muslim cannot marry a non-Christian, neither permanently nor temporarily. Regarding a Christian woman, there are two opinions, the more apparent being that it is permissible temporarily, and even permanently, although it is advisable not to neglect caution (and one should not marry a Christian woman without the consent of the Muslim wife).
Grand Ayatollah Sayyid Zanjani (may Allah protect him):
It appears that a Muslim marrying a Jewish or Christian woman—whether permanently or temporarily—is not invalid, but it is contrary to recommended caution and is also disliked in permanent marriage.
May you be successful in all good.