Masters degree without a Bachelor at all, or Masters degree after having a Bachelor from an unrelated field?
I think the first one is strictly impossible. So far, I have never heard of someone getting a Master before having the Bachelor first.
I know there might be corner-cases for geniuses who do both at the same time, or get directly accepted to phd studies skipping everything. But that is highly unlikely in usual cases of regular people.
If you have such a goal, it will be a massive administrative obstacle to overcome. And I don't see how you could convince an established university to give up their requirements.
Maybe in 3rd world countries you can get any type of degree by throwing some money, but it does not seem to me as if that is your goal.
EDIT (after @Mad Jack's comment below): Yeah there are always corner-cases which may change the story. Given that your experience is worth more than a undegrad diploma, or the fact that you might hold different certificates might give you a chance. But, then again you will have to ask the admission office to make an exception for you. Tough, but not impossible as I learned something new!