Technically it's actually Madam Red's jacket, unless you're talking about his younger Reaper jacket. With no ref pic I'm going to assume it's the red one he wears off the shoulder, also indicating it's not his since it doesn't actually fit him.
I know a lot of people without sewing experience hit up Goodwill/thrift stores and such to find something similar that can be modified. If you were going to try this I'd do it soon as the winter months will be really the only time for any luck.
If you're dead set on making it I agree with looking at the commercial brand patterns, be it online or at your local fabric store. I'm not entirely sure I agree with the mens pattern thing but I would say look through both. I do think that Simplicity 1732
looks really close you would just not add the detailing stuff in those pictures. I would use view A for the actually Jacket but go more with the length of view B.
Now if you're talking about the black reaper jacket disregard that but more people might be able to help if you specify and provide a picture.