You could get an Sh.18 carb and some 10x13mm aluminum tube, cut the tubing to the length of the neck, and epoxy it onto the carb as an adapter. Would cost under $30 altogether, and I've had great results with that carb. Did that exact thing with that carb + 12mm tube to make it fit a racing...
I think basically your only option is the OS 11k, which is a bit pricey. The plus side is, it's an amazing carburetor, the best out there.
The Losi 3.4 Carburetor is also a fit, but those are long-since discontinued.