first of all thank you for your tips.
The "ktm mechanic", (his name is Ratna), is from the ArKa shop mentioned by Chris in Tokyo.
He then introduce me to a guy that has at least 6 or 7 unused, semi-incomplete Bmw 650 Funduro in a warehouse behind a closed door... just 500m from the Oasis.
So I ended up buying a brand new Funduro rear shock (it was still in the bmw cardboard paper package, directly from Berlin...) that seems to fit the GS, a new DID chain, a clutch cable, and some bearings.
And I am ready to go again.
As for the WP suspension, I wrote an email to Austria, still no answer.
I don't know why it broke.
Here's what happened:
1 the bike started to bottoming, the tire hitting the mudguard
(I think there was some leak in the preload adjuster cable, so there was no preload)
2 I increase compression to avoid it
3 In a really slow corrugation track the bolt that hold the bottom of the shock broke.
4 One of the WP shock washers was worn out, and I replace it for another one but not the same size. So the new bolt was thinner than the original.
5 Almost 1000k later the suspension broke. First on one side, 2 or 3 km later the other side also broke, destroying also the bearing in the deflection lever.
6 I couldn't go anywhere.
7 1 minute later I got a lift from a very nice mongolian couple that brought me to UB.
Now, a bit tired of the Oasis burgers,
it's time for Russia again, and the Baikal.
Once again thanks