I always use this micro servo. It's plenty powerful.
https://www.amainhobbies.com/ecopower-827-12g-digital-metal-gear-micro-servo-high-voltage-ecp-827/p1310408
If it were me, I'd just cut that off and splice in a regular JR (Futaba style) connector. Adding an adaptor just adds to the clutter. I keep a slew of servo extensions around just for doing stuff like that. Just curious, what servo did you get?