I think what y'all should do first is sit down and do some reading here.
I think you'll learn a lot about swinging in general how to find what you're looking for. You're right, it's not something to rush into in a bar somewhere; there are things that you and your boyfriend should think and talk about. Your quest is not uncommon and I'd suggest using the Search feature on the board to look for threads discussing the subject. If you need help with that, just ask.
The thing is, single bi-females are scarce. What Mr. Spoomonkey suggests is probably where you'll find the most success, unless your boyfriend has reservations about sharing you with another man. You'll need to talk to him about that, should you decide to take that route.
Most of all though, take it slowly. As you learn more, you'll more than likely figure out what will work for you.
BTW, are you the one who posted a similar question as 'Unregistered'? If so, I'll remove that post, so that all replies will go here in one place. Thanks!
-B