Another vote for the Stubben Genesis Special D. It is new technology for the flexible tree with the closeness and plain flap of the Schulteis. Four billets and the overgirth strap give it thetraditional look with great versatility for balancing.
Fatorange, You may be in luck! Stubben has some used/demo saddles for sale on their website. They have several Tristan Specials (Schultheis w/o blocks) in brown for sale. Just what you are looking for. They have the flexible spring tree and are listed for $995.00. If the saddle doesn't have the billeting system you want, you can have the billets changed. My Tristan Special is out right now to have a point billet added. It is several years old and much more comfortable than my vintage Tristan (circa 50's/60's) that has a wooden tree. A bargain!! Hope they have what you want.
I don't know of one for sale other than the two on Stubben's site (and they're new, not used), but I know I ran across a couple of them when I was looking to buy older Stubbens. Most of the time they're just called Tristans and you have to look at the specs to see what they actually are.
Hi - not sure if you're still in the market, but I have two original Stubben Schultheis saddles for sale. They are both 18", one is a havana brown and the other is black. I'll have to look and see what the tree size is on them. Great saddles, just I have two toddlers to run after right now and no plans to get back into dressage in the near future. Can e-mail pictures. I'm located in SK, Canada.