Another option is to buy a scrap vehicle for spares, particularly if it is rotten, break this, use the spares you need, keep the ones you want, and sell off the rest.
Many people who i know do this usually make a profit as well as getting a stock of spares for future use.

Sounds a bit like the end of that diff but look on ebay for one being broken and replace the lot. Bear in mind that they are heavy so to collect you will need a few strong hands and a preferably an old Pickup or the like.

OLDMINIMAN