I won't post the seller's name or a direct link to the product, because that's probably against the forum rules, but simply go to Ebay France
http://www.ebay.fr/ and search for "orange prepaid 15". The seller I used had more than 2000 positive feedback. He is obviously used to selling to foreigners because the item description is in English.
The seller is now selling micro-sims as well as regular sized sims with the 15 euros credit. Note that the item description says that you need 12 euros for the Internet Max - this is incorrect - it's now only 9 euros.