Have you thought about swapping front and rear diffs around?
Put the locked one in the front until you get your hands on a LSD unit.
I'd be expecting to pay $3-400 for a LSD diff privately, more through a wrecker.
I have a 4.3 Open that you culd have to get the warrant then find an LSD later??? Pity its in Chch. I got a diff down from up that way not long ago and it didn't cost that much. Don't want that much for the diffhead. If you keen on the idea, make an offer?
Cheers Daniel