I don't know if what you say is true, ie that there are more 2 male 1 female relationships on here. Maybe there are more Vs like that but I would think MFF triads are more common.
You sound like my partner and he is experiencing the same frustrations. He does have an intimate (non-sexual) relationship with a long distance love but she only partially fills his need. He would like someone to be part of our life on a regular basis. He says the only time he has ever felt totally complete was when we were staying with his other and we both cuddled up with him in bed.
I have a theory that maybe his need comes from a rather insecure childhood where he was raised by his mother and older sister (his sister was more nurturing than his mother, but she married and moved away when he was only five) Any similarity with you?
Perhaps understandably it takes a very special woman to knowingly go into either a V relationship or a triad. Bi-sexual women are the most likely contenders. Maybe you could seek out one bi-sexual woman first and then both seek another?
best of luck