All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
If you are still married to this man, we advise you to return to him and accept his condition above all that it is a temporary condition. Maybe, he would marry soon and accept to have children with you. You may still try to convince him to let you conceive without conditions. Seek the Help of Allah, ask Allah to make him accept your demand. You can also seek the help of an intermediator whom you think has some influence on him like one of his parents.
On the other hand, know dear sister, that we do not know any specific Du'aa’ (supplication) that should be said in such circumstance, neither do we know any specific Soorah that should be recited in this situation. But make general Du'aa’.
If your separation from him was through divorce, then it might be better for you. We hope that Allah will give you a pious husband who would meet your desires without conditions. But if you want this man only, then you may talk to him but not in seclusion and express your desire to return to him and accept his condition. When you return to wedlock life, there is no harm that you ask him to let you have children from him without conditions.
For more benefit that the husband has no right to deprive his wife from having children, please refer to Fataawa 385597, 195927, 278053, 87397, 101099, and 84472.
Allah knows best.