Had a MMF threesome want a MFF threesome but...

I've had a threesome with my husband and it was fine. The other guy rather sucked in bed but I felt so close to my husband afterwards for months. We would both like to have a threesome with a woman but I just dont know how to find a girl thatd make sure to prevent pregnancy and if itd occurred to either give us the child or give it up because we will not be having kids with others.