If it is the removable case cover, drain the oil/trans fluid, and remove it. Find a reputable licensed Heli-arc Welder that specializes in aluminum welding, have him/her weld the crack shut, and to do what's necessary to repair and restore that part. It may cost a few $$$, but it is worth it compared to the hassle you'll have trying to find one. A good welder can make the piece look new. A little grinding, and polishing on a metal buffing lathe, and it'll be good to go. I used to do this type with my eyes closed; [semi retired due to health issues].
That's makes two questions I have answered for you on this 550GS.
I'll keep an eye out for more.
I usually hang in cooking & recipes.
Happy Holidays!
