The servo rudder you are looking for is here, all sizes and mounting types are available!
Reference 09C-10122
Brand: CORALLY
TEAM CORALLY - SERVO SAVER - LARGE - UNIVERSAL - DOUBLE END - C-10122
Reference 09C-10123
Brand: CORALLY
TEAM CORALLY - SERVO SAVER - LARGE - UNIVERSAL - NARROW END - C-10123
Reference 09C-10124
Brand: CORALLY
TEAM CORALLY - SERVO SAVER - H D LARGE - UNIVERSAL - 23-24-25 - C-101
Reference 09C-10131
Brand: CORALLY
TEAM CORALLY - SERVO SAVER - SMALL - 24 SPLINE - HITEC - C-10131
Reference 05FAST310B
Brand: FASTRAX
23T BLACK ALUMINIUM SERVO HORN (KO/SANWA) - FAST310B
Reference 02RC15202-BLU
Brand: RC PARTS
ALUMINUM SERVO HORN BLUE (25T - 31mm) - RC15202-BLU