Weyermann does make a smoke extract
HERE. Check out the wholesalers tab or call direct.
Here's my all grain recipe for a good rauchbier.
98% Weyermann Smoked, 2% Weyermann Carafa II Special dehusked, Hallertau, and WLP820.
You would think that the above recipe would be too smokey, but i would say its about 50% as smokey as Schlenkela Marzen, and nowhere near the Urbock. The reason, i read somewhere that Schlenkerla does not use the Weyermann rauchmalt (a pilsner malt) that we get here, but a proprietary smoked munich malt that is much smokier.
You could also try using Briess Cherrywood, maybe it will impart more smoke to the final product. Check out this
THREAD.