Are you meeting people on a dating site? Or in real life?
On dating sites you can let people know EXACTLY what is going on for you before even meeting them, ie, "I am bi, married and looking for a bi woman to be a girlfriend in a poly-fi situation."
If not then I suppose you could just be cautious and do your best to not get invested until the woman knows exactly what is going on and agrees to it.
You do sound more poly-fi to me than anything else... what you seek does exist and is out there... I live in a more poly-fi situation for example... I live with two men, have a girlfriend and another boyfriend...
Anyone want to be friends on Facebook?
Send me your name via PM