The great thing about an MBA is that you can decide where you'd like to specialize as you go through courses. But as far as an MBA in Fashion Management, I don't think I've ever heard of one. You might consider contacting FIDM in Los Angeles, and see what they might recommed.
But if you are trying to creat your own company, you may consider an MBA with a concentration in entrepreneurial studies. This will teach you how to create, run, manage, grow, etc.. your own business. This might be just what you're looking for.
Good luck!