Jenwife, you hve already made the decision to find a black lover to enjoy long term. I feel it in your words and in the way you pick out which photo to post.
Your husband now knows your fantasy - and that you want to live your fantssy, so let it "sink" into his mind over a fw months, and occassionally mention how you are wanting it more and more.
And ask him if about his secret fantasies as you have told him yours. Build his fantasy over several weeks or months by talking about it a lot - and suggest that if he lets you have your fantasy, then you will help him have his.
Talk to him about how much you want to stay married to him, but the curioisty to be with a black man has become something you think about a lot.
And if he enjoys himself with another woman, then it will help you to enjoy being with anothe man - as both of you are equal and can swap notes on how each other's date went.
Most times, it is better not to encourage a husband to fuck another women, but it might be the only way your husband can handle your situation. Once he has slipped his penis into another female and ejaculated, he will realise how lucky he is to have a wife like you who is willing to share.
Think of extra-marital sex as a gift you both give each other, as long as it is with someone who is healthy and free from STD nasties. Your husband needs to feel your love, and also your desire to give him the gift of kissing another woman's pussy slit. You are trying to talk him into a fling with another woman rather than trying to beg for your fantasy to get fuel. Tease him about what it might be like for him in bed with another female and how contented he will feel afterwards.
Once he has fucked another female with your permission and encouragement, you will be able to get all the big cock that is on offer to your heart's content.
Pushing him into bed might be a lot easier than you trying to get permision for your own needs.
Be patient and just keep building up the fantasy for him to be with another woman; and you might like to watch him do it if he doesn't mind you being there.