The only way I know to get parts is to scavenge them off of broken diffs. That's why a lot of people go to aftermarket when they break. FYI, the front is supposedly stronger than the rear because some parts are thinner in the rear to accommodate the limited slip that works when the locker is unlocked. Many people put a front diff in the rear when they break a rear diff.
Ask on pirate and you may be able to find some parts cheap.