There is a notable discrepancy in the number of single women in shidduchim versus the notably lower number of single men in shidduchim.
There are women who would agree to be part of a family with multiple wives were that a viable option. There’s even a longtime member of this coffee room who is an older single that posted here she’d be open to the idea.
It is legal in some countries, including South Africa (which has a frum community and the President of the country himself has multiple wives.) So anyone could visit South Africa to do it should they so desire. And America has accepted tens of thousands of African immigrants with their multiple wives, many of whom live in New York City.
Additionally, Fundamentalist Mormans have openly been practicing polygamy in the United States for hundreds of years and continue to openly do so today. Court decisions have protected them from being adversely affected from on the books marriage restrictions and even more recent court decisions have made clear the entire US laws precluding polygamy, even though they aren’t enforced and haven’t been in nearly a century, are unconstitutional in any event.