So you would like to build your own omnidirectional robot? The Moebius Mecanum Wheel Robot Kit has you covered. It has a 10.24*9.06*2.56inch platform and can bear up to 10kg. It also has 80mm mecanum wheels that are hard to damage.
This robot car can turn on a dime. It has 4 12V 330rpm motors. You can use this kit with your Raspberry Pi, micro:bit or Arduino.