Well I think what you may need to do now is start the hunt. I would suggest if you are looking for a woman first to share. By sharing you don't have to always have threesomes. If you are bisexual, you could have a relationship with this woman and the three of you casual have threesomes. My gf and my husband do boy have a sexual relationship, they do love and care for each other though. But every once in awhile we have a threesome and its mainly my husband pleasing me and me pleasing my gf.
I would also suggest if that is something you want, sharing a gf, that you as the woman should put yourself out there. Its much harder for a man to attract a woman into all ready stable relationship. I think part of it maybe we as woman wonder if the other woman is really ok with the situation. Also you as a woman will look less threatening.
If you are going to use dating websites, I used okcupid and just thoroughly explained my situation and what I was thinking for and what I needed for the other person. There are poly websites but the volume of people on them us very small compared to other sites. And to be honest I meet several poly people on there that happened to even be local.
I hope they helps