So you would like to build your own robot with mecanum wheels? This 20kg Mecanum Wheel Robot Chassis is worth a look. It can be used to make a 2/4WD smart robot car with omnidirectional wheels. It has a 4-channel driver board. The chassis is driven by 78mm steel mecanum wheels.
The kit ships with wheels, motors with encoder, driver board, PS2 controller, and everything you need to get started. As the name suggests, the chassis has 20kg payload capacity.