Those gearcases come as a “matched” set. They are machined and bored together. If yours is cracked due to freezing, just have it welded. Sand down the weld, paint it and it will be barely noticed. Now I have seen some mismatched lower halves mated with different upper cases so if you are lucky, you might be able to get one to work. Now if the skeg is broke off and in need of repair, take it to your local prop repair shop and they might be able to weld a new skeg on for you.