Hi Fabien,
You can still order an original replacement part directly from us. We charge $15 for this part. Please note this is the only part we use that requires a metric nut driver, but that shouldn't be a problem for you in France.
The easiest way to order is to send me an email with your exact shipping address the way you want it to appear on the label along with the serial number of your Alembic and the list of parts you need. Then you can call our office or fax your credit card details for payment. It's best not to send payment details by email.