I think XYZ123 is on the right path. Your best bet may be in the industry itself since you will
probably be dealing with nonmonogamous partners. Otherwise, if you meet a single woman, you have several issues that have to be met. She has to be bisexual, attracted to you and your wife (I am assuming you are a married MF couple), be ok with you being in the sex industry and be open to polyamory.
To increase your odds, you could also consider married women who are into polyamory and would be open to dating you and your wife. Or just work on the "V" model where you or her look to date someone in a more one on one sense and see if it leads to a triad or threesomes.