I took parts from an old radio controlled toy. It was a rather sophisticated army tank and it had these gears in it as well as some others.

The two shafts should be just right. I will eventually add cams and cranks to these shafts to provide the necessary movements. I have two bevel gears to change rotary movement 90 degrees. I’ll try to drive a single longer shaft from one of these and then use that for cams and cranks for side to side movement.