Here's my attempt at repairing the old cyber master brick.
The motors are quite small and out of nine units that i have, seven don't even work anymore.
I found these motors on amazon and put the grey gear from the internal gearbox on it. I had to cut off the decoder part of the gear due to space limitations.
Looks like a perfect fit :) Need to cut into the battery compartment, but that shouldn't affect the end result (will install small LiPO battery).
That's it for now. Need to order new ca glue to continue^^