This is what we were looking for when we joined the site. A cuckquean discussion. Me and my girlfriend are exploring this area as she suggested it and regularly suggests we find another female to bring in for me to play around with while she watches and/or listens. It is also rather hard to find a female easily joined into the scenario. She's even pushed forwards towards a poly amorous type situation suggesting sex and emotional involvement with another. She's highly expressed no desire for other men and we've talked about that multiple times over the course of this last year. But, as the sub she is, she would most definitely do as I say - if I did want another male in the situation. She lives to please. Most amazing woman I've ever been with, to say it shortly.
But again, like Cuckqueanhubby mentioned: finding someone outside your normal circle (on a professional level) is hard to do. Although, we do frequent strip clubs and have made some friends here and there - explored lightly but haven't had our desires totally fulfilled.