Why not preach in the streets? Show people that they can have their sins forgiven if they call upon the name of Jesus, Jesus can forgive them. Then you can invite them to church, and from there explain that in that church there is the option, if they so choose for that kind of marriage. But I think the search for a wife should be subordinated to the preaching of the Gospel of God's love.
You want, also, to marry a Christian.
Since I see polygamy as a help for women who are orphans of society, I think... why not marry "call girls"?
Maybe you can take half of them off the market
There are many lovely ladies who are orphans of society, who are being used and abused by human-traffickers. And sometimes have problems with addictions, etc.
Giving them money won't help, they would probably use it for drugs. Also you can't spill your children's inheritance so easily for strangers.
A home is what they need. I have this idea, if someone is willing to do it: To witness to "call girls" and show them they have an option, maybe they need rehab or something. If a girl has gone through so much pain that she is humble enough to consider the idea of plural marriage, would you forgive her past? There are plenty of good looking "call girls" who need a home.
When Jesus came, it was not the religious people who were most keen on accepting Him. It was the harlots and tax collectors.
If there is one group of women in danger, it is them, "call girls". I see polygamy as a way to help women find a home, more than a way to help men have sexual variety. (For that, you better abandon Christianity and become a normal fornicator... there are cheaper ways to have sexual variety than polygamy).
Yes, I think you would do a favour to a woman, by snatching her from a "pimp" and placing her in your family. Of course, if she accepts Christ, if she confesses and forsakes her sins, if she is washed in the blood.
Now, this may seem like an extreme idea, but I have a thought that may show it's not so extreme:
Most women of today's society, by age 20, qualify as guilty of "harlotry" by Deuteronomy 20:21 standards.
Girls who have had sex before marriage are condemned to death, in the Bible.
Not so harlots. Solomon judged between the two harlots who were disputing a child's motherhood. And they were not put to death for being harlots.
Rahab was a harlot, but when she was washed in the blood, she even became an ancestor of David, and of the Saviour.