You can buy JIS French thread bottom brackets brand new from
velo-orange.
From your description I'm not sure if you were planning to go with a modern 102mm cartridge or just older loose ball cups. If it's just cups you want, I've found Sugino french cups on ebay for very reasonable prices (<$20).
But if you really want modern Campy, you can have the BB rethreaded Italian. You can't just force the cups in. Add a 2mm spacer (mine's on the drive side on my conversion) and you're good to go.
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