i really dont have a good answer for you, but you may be able to attach it with a double sided screw. depending on how the break was if it was diagnal or straight. I would recommend calling around to some of the well known taxidermists in your area and asking them about it. You may can even take it in and see what they tell you. Even if they are not going to do the work for you, unless they are real jerks, should tell you what you need to do the job and where to get it at.
good luck