I think that failure is not so uncommon in the D2 spec diffs. You might be able to get the parts from someone who has fitted a locker. Hopefully the hemisphere is a straight forward and relatively cheap fix if thats what you're after.
If that part has failed though, make sure you check carefully the half shafts and CV's as they're all pretty close in strength and you may find there is twisting in them. If they're twisted you're due for them also.

