There is one on Ebay (US) right now, complete with mounts, at $475.00 USD 'or best offer'.
It's been listed for a while, perhaps seller will negotiate price? Kahles Snapper Ebay

Listing indicates that he only ships to the United States, but If he won't ship to France a member here may be able to assist.

I've assisted with shipment of catalogues and such to Australia. If it's legal and the customs paperwork isn't too annoying I might help you out (expenses paid by you, of course).

You may also consider contacting member and Saxon Forester, Kuduae.
He is closer to you geographically, is very knowledegable of Mannlicher Schoenauers, and may be aware of sources for such parts.