In my opinion, which is long a legal opinion, if you are not making it for profit and only doing one for yourself I wouldn't worry about it. They will not bother to come after you. If however you are making it for profit you better get permission in writing.
As in art work there is also a fuzzy line. If you are not making an exact copy you may be ok. Again, I'm no lawyer. It's kinda like it's against the law to go over the speed limit but they're not going to pull you over for one or two miles over the speed limit but they could. It's your risk.
If I were making it for myself I probably would go for it.
Art