You could have a nice try on XQ-S3008D
Here below is the specifications:
SIZE:40.9*20*25.2
WEIGHT:56g
SPEED:0.12sec/60° at 4.8V
SPEED:0.1sec/60° at 6.0V
TORQUE: (97 oz-in)7kg/4.8V
TORQUE: (111 oz-in)8kg/6.0V
Voltage:4.8-6.0V
Dual ball bearing,metal gear and coreless motor