OKCupid is the best site for finding polyfolk, it appears. And most of the ladies don't look like Hooters girls--not that such matters to a great many people, anyway. I suspect you'll be able to find suitable people on there.
Unicorn hunting is likely to be frustrating, though, as there aren't many unicorns to be found. There are plenty of bi babes who could end up involved with a couple, sure. There just aren't many who are single and specifically looking for a couple. I'll suggest looking for a person instead of a unicorn.
When speaking of various forms of non-monogamy...it ain't poly if you're just fucking around.
While polyamory, open relationships, and swinging are all distinctly different approaches to non-monogamy, they are not mutually exlusive. Folks can, and some do, engage in more than one of them at a time--and it's all good.