The new housings are generally a tad bit smaller than the old, so you might be able to use the old ferrules with new housing. Take a ferrule or two to your LBS and see.

The biggest deal is to ensure you have a proper seat at both ends and the correct ferrule will guarantee that seat.

Yeah, Ebay would be your best bet for fiddly bits - not that you should need them if you've not tossed your original ferrules.

DD