To hopefully help you find what you want, maybe you could give a little more information about the person you are seeking, other than the fact that they need to be female (which I am assuming from the use of the term "sister wife").
What age range would you consider?
Can the person have children?
Must the person be single?
Would it be ok if, later on, they were to also date another person?
What sexual orientations would you consider? (Heterosexual, bisexual, etc)
Do you have any preferences on things like smoking, drinking, recreational, drugs?
It is ok if she has pets, like dogs and cats?
How far from you should the person live?
and maybe a little more about you two - what activities do you enjoy? Do you have pets, etc...
I am sure you get the idea. Hopefully more information will help you find the person that you are looking for.
I wish you luck.
"Listen, or your tongue will make you deaf." - Native American Proverb