If they are loose ball type, and not a cartridge sealed bearing, @easyupbug is spot on, IMHO. Take caution though, even doing the Grade 25 can get silly in their prices, if you are looking to stay with NOS/NIB Campagnolo bearings though. Lots of listings for loose balls on-line, at eBay, and you can find them at a home improvement box, or hardware store as well, in the various necessary sizes. Just exercise due diligence about low ball offerings and the big bulk sales, these can be iffy in their quality and consistency.

Bill