I have a tig at home and have welded several of these with great success. It is important to make sure it is absolutely clean. Wash the part thoroughly, then heat the cracked area to boil out the rest of the oil residue. Use a small propane torch or even a heat gun. Wipe with acetone or lacquer thinner and repeat the process several times until nothing else boils out.
Take a very small drill bit and drill a hole on both ends of the crack. This will prevent the crack from spreading. You can also take a small die grinder or Dremel and grind a groove right along the crack. Heliarc it and away you go. Any competent welder can handle this. Make sure he welds both the inside and out. Finally file down the outside weld and polish it. Good as new.
Or buy one on ebay and hope it's not cracked either

BTW you will need to pull the stator windings out!