Hi Jimmy,
Pololu - 34:1 Metal Gearmotor 25Dx64L mm LP 6V with 48 CPR Encoder (No End Cap) - these motors will be good if you would like to build your own version of Ralph. You will also need this IMU: MPU9250.
If you prefer to use assembled Ralph, you can still buy this at https://store.husarion.com/us/home/9-ralph-kit.html . This is a new generation of Ralph, based on CORE2 robot controller - successor of RoboCORE. Instructions how to assemble this you will find here: - YouTube .
Have a great day!
Best,
Dominik