You need to find yourself a bull with a good reputation with other hotwives and one that doesn't mind proving he has a clean bill of health. When you do find a reputable bull, and the deed is dandy, he'll hook you up with other reliable contacts. Of course, it is your responsibility to be checked out yourself on a regular basis because you cannot rule out the possibility for your health's sake.
Don't let the safety issue take the shine of your eagerness, it should part of the erotic build-up to being taken by a black python. Over time, you will enjoy unprotected sex with bulls you trust.