LEGO TECHNIC 60-Piece GEAR, Wheel, Axle and Stopper Pack Set bushing bush differential turntable motor part EV3 NXT : Everything Else - Amazon.com
Bricks and Gears 10712 | Classic | Buy online at the Official LEGO® Shop US
LEGO 46pc Technic gear & axle SET (Works with Mindstorms NXT, EV3, Bionicles and more LEGO creations!)
Technic Construction Parts | Truck Accessories Set | Gear Cross Axles Pin - 650pcs Car - Aliexpress
46pcs Technical Linear Actuator Pro Kit Cylinder Piston Power Functions Robot Car Gear Axle Set Compatible with Lego 61904 92693|Model Building Kits| - AliExpress
DC Gearbox TT Motor to LEGO® compatible Cross Axle : ID 3810 : $3.95 : Adafruit Industries, Unique & fun DIY electronics and kits