Is the nipple welded into the tank broken, or is it the fitting?
If it's the nipple, you may be able to get a blind bulkhead fitting and ream the hole out and put the bulkhead in it's place. Blind Bulkhead Fittings
If it's the welded nipple and you can't get a bulkhead fitting in there, then you'll likely have to replace the tank. Those nozzles are spun welded into the tank wall, and there's almost no glue that will stick to the plastic.