We found ours on OKC after a LOT of searching.
Many of our requirements are the same as others have said - hung (8"+++), tall, in shape, capable of an ongoing conversation / dating; STD free (bare back only), and reliable for ongoing Bull sessions. Also had to accept and support and understand that the husband in our case is the Stag and the ultimate master with full veto power. The Bull is Dom in the bedroom, but everything is out of submissive's hands. Finally found the right fit after a LOT of flakes.
OKC seems to be very open to open / poly relationships with a good mix of true black Bulls.