Fetlife and OKcupid tend to have lots of poly people. However, the way that they tend to see things is often pretty different than swingers so proceed with caution and read up a lot on polyamory.
As far as finding a male in general, I think it is often difficult to find good ones regardless. Some lifestyle SM's would be interested. Some couples might be too for that matter depending on their rules. I mean if a guy in a couple started dating you, that would let his wife be a unicorn able to do whatever.