RC Mini-Servo (9 grams) with mounting Kit for NXT/Ev3

This kind of micro servos can be used for helicopter, airplane, car and boat. It owns high quality and high cost performance. In the meanwhile, it is light weight and has a small size. I believe it is a good tool for you.

Beffkkip 4pcs SG90 9g Micro Servos for RC Robot Helicopter Airplane Controls Car Boat

S3003 Standard Servo RC Servo High Speed for RC Racing - AliExpress

Proof-of-concept Robot Arm and Controls (Lego Nxt) : 5 Steps - Instructables

DIYmalls Feetech FS90R 360 Degree Continuous Rotation Micro RC Servo Motor 6V for Arduino Microbit Smart Car Robot (Pack of 2) : Toys & Games

This kit contains a very compact, light duty servo motor, mounting plates, horn plates and mounting hardware to integrate it with your NXT/EV3

RC Mini-Servo (9 grams) with mounting Kit for NXT/Ev3

What is a better way than Lego Mindstorms to get my child started with robotics? - Quora

FK Engineering's Blog: 2016

Buy DIYmalls Feetech FS90R 360 Degree Continuous Rotation Micro RC Servo Motor 6V for Arduino Microbit Smart Car Robot (Pack of 2): Servos

DIYmalls Feetech FS90R 360 Degree Continuous Rotation Micro RC Servo Motor 6V for Arduino Microbit Smart Car Robot (Pack of 2)

DIYmalls Feetech FS90R 360 Degree Continuous Rotation Micro RC Servo Motor 6V for Arduino Microbit Smart Car Robot (Pack of 2) : Toys & Games